e1209

					                                                                                                    End-User Support:Operating Systems




                           Understanding
                            The Registry
              Editing the registry is not as hard as you might think, but you need to understand
                 what you’re doing, and it’s essential to make a backup before you make any
                              changes so that you can back them out if necessary.

                                                                                                                         By Mike Lewis




    P       ut simply, the Windows registry
            is a central repository of infor-
            mation about all aspects of the
    computer - in particular, its hardware,
                                                   The registry has several advantages
                                                over INI files. Because the information
                                                is centralised, it is easier for applica-
                                                tions to access it. It is more hierarchical
                                                                                              registry is spread over a series of files,
                                                                                              sometimes called hives.
                                                                                                  SYSTEM.DAT and USER.DAT are
                                                                                              usually held in the Windows directory.
    operating system, applications and us-      than INI files, and so better suited for      However, it is also possible to place
    ers. It can be accessed and updated         storing large amounts of structured           USER.DAT in the user’s login direc-
    under software control and also di-         data. It is also free of the size limita-     tory on a network, thus allowing the
    rectly by users.                            tions which affect INI files (although        user to log in at other workstations. In
        The registry first appeared in Win-     there is still a maximum total registry       NT, the hive files are located in the
    dows 3.1. In that system it was a single    size limit).                                  SYSTEM32\CONFIG directory, which
    file, called REG.DAT, and was mainly                                                      is off the Windows directory.
    used to store information about OLE         Storage
    objects. Most other configuration data                                                    Architecture
    was held in various INI files, of which         Although the registry is usually
    WIN.INI and SYSTEM.INI were the             considered to be a single entity, its con-        When you view the registry in the
    most important.                             tents are in fact stored in more than one     Microsoft Registry Editor its hierarchi-
        The modern registry, as found in        physical file. In Windows 9x, there are       cal nature becomes obvious. (To
    Windows 9x and NT, brings together          two such files: SYSTEM.DAT and                launch the editor, run REGEDIT.EXE
    all the information that was previously     USER.DAT. These hold computer-spe-            from the Start/Run menu. I’ll describe
    held in REG.DAT and the separate INI        cific and user-specific information re-       it in more detail later in the article.) The
    files.                                      spectively. In Windows NT, the                editor presents an Explorer-like view
                                                                                              of the registry, with a tree in the left
                                                                                              pane and data in the right (see Figure
                                                                                              1).
                                                                                                  The registry tree is divided into six
                                                                                              broad sections (five in NT). These sec-
                                                                                              tions, which all have names beginning
                                                                                              with HKEY_, are called root keys or
                                                                                              top-level keys (see Figure 2). Each root
                                                                                              key contains sub-keys, which might in
                                                                                              turn contain further sub-keys and so
                                                                                              on. The lowest level keys along a given
                                                                                              branch are called values.
                                                                                                  Taking a hard disk as an analogy,
                                                                                              keys are like directories and values are
                                                                                              like files. Keys and values both hold
                                                                                              data, which can either be binary values
                                                                                              or ASCII strings.
                                                                                                  Each item of data has an associated
                                                                                              name. As a minimum, each key and
                                                                                              value holds a single data item, named
             Figure 1 - The Microsoft Registry Editor shows the registry’s                    Default. The data and names are dis-
                                hierarchical structure.                                       played in the right pane of the editor,



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     along with an icon which shows                alias for HKEY_LOCAL_MACH-                    cludes REGEDIT.EXE, although this
     whether the data is binary or string.         INE\Software\Classes.                         might not be the same as the one found
        Continuing with the hard disk anal-           An alias is not a copy. Rather, it is      in Windows 9x. If you upgraded from
     ogy, you can identify any key or value        another view of the same information.         Windows 3.1 to Windows NT, you will
     by specifying the path along its branch,      If you edit the data in the alias, the        have the original 3.1 version of RE-
     using the familiar backslash notation.        change is immediately reflected in the        GEDIT.EXE.
     For example, information about in-            part of the tree to which the alias refers,       As far as the Windows 9x version is
     stalled dial-up networking connec-            and vice versa. Only one edit actually        concerned, its operation is completely
     tions is held in HKEY_CUR-                    takes place, but you are seeing it from       straightforward, with all its functions
     RENT_USER\RemoteAccess\Addre-                 two different viewpoints. Figure 3 lists      being easily accessible from the regis-
     sses. If you drill down through this          the aliases in the Windows 9x registry.       try and Edit menus. You can also right-
     path in the left pane, you will see the          One       of     the     root     keys,    click on an item to edit, delete or
     relevant data in the right pane. In this      HKEY_DYN_DATA, works slightly                 rename it, or to create new keys or
     example, each data item corresponds           differently. This key is essentially a        values.
     to one DUN connection.                        RAM-resident copy of certain parts of             When you edit a data item in the
                                                   the registry which Windows needs to           editor, the change is written to the reg-
     Aliases                                       get at quickly. It is created at boot time    istry almost immediately - you do not
                                                   and discarded at shut-down; it never          explicitly save the file. If you make a
        I said earlier that the registry is di-    gets written back to disk.                    mistake, the only recourse (apart from
     vided into six broad sections, one for           Because aliases only exist while           restoring from a backup) is to edit the
     each root key. This is certainly how the      Windows is running, they will not get         same item again.
     registry is usually regarded, but it is       backed up if you create your backup               Conversely, if another process
     not strictly true. The reason is that all     copies from DOS. This is not a problem        changes a registry item while the edi-
     but two of the root keys are in fact          as the information in the aliases is all      tor is open, the editor will pick up the
     aliases for other parts of the tree.          available elsewhere in the registry.          new setting straight away - although
        To see an example of this, drill           Windows always re-creates the aliases         you might need to refresh the display
     down from HKEY_CLASSES_ROOT.                  during startup.                               in order to see it (to do so, select View,
     You will see that this root key contains                                                    Refresh, or press F5).
     a large number - perhaps many hun-            Registry Editors
     dreds - of sub-keys at the first level                                                      Remote Registries
     down. The first group of these sub-              The main tool for viewing and edit-
     keys have names which look like file          ing the registry is the Microsoft Regis-          As well as letting you view and edit
     extensions, while the names of the re-        try Editor, REGEDIT.EXE. Although             the registry on your local machine, the
     mainder resemble those of applica-            third-party editors exist, you will           Microsoft Registry Editor can also ac-
     tions.                                        probably want to stick with the official      cess registries on other computers on
        Now locate HKEY_LOCAL_MA-                  Microsoft product, given the critical         the network. If your machine and the
     CHINE\Software\Classes. As you                nature of the registry editing process.       remote computer are both running NT
     can see, this contains exactly the same       (That’s not to say that REGEDIT.EXE           4.0, this operation is completely
     sub-keys, values and data as                  is itself completely reliable; the Mi-        straightforward. But if either or both
     HKEY_CLASSES_ROOT. That’s be-                 crosoft Knowledge Base notes several          machines have Windows 9x, you must
     cause HKEY_CLASSES_ROOT is an                 bugs in the Windows 95 version, but           first install the Remote Registry serv-
                                                   these are unlikely to cause problems in       ice, which in turn depends on having
                                                   day-to-day operations.)                       user-level security enabled and Re-
       HKEY_CLASSES_ROOT                              Windows NT 4.0 comes with a sec-           mote Administration services in-
       HKEY_CURRENT_USER                           ond editor: REGEDT32.EXE. This sup-           stalled. For step-by-step instructions
       HKEY_LOCAL_MACHINE                          ports certain NT-specific features            on setting this up, see Article Q141460
       HKEY_USERS
                                                   which REGEDIT.EXE does not know               in the Microsoft Knowledge Base.
       HKEY_CURRENT_CONFIG
       HKEY_DYN_DATA                               about, such as the ability to maintain            Once you have installed the neces-
                                                   security settings. However, it lacks the      sary components, you can access the
                                                   very useful search function found in          other computer’s registry by selecting
           Figure 2 - The six root keys.           the standard version. NT 4.0 also in-         Connect Network Registry from the


       Root key                                   Alias for
       HKEY_CLASSES_ROOT                          HKEY_LOCAL_MACHINE\Software\Classes
       HKEY_CURRENT_USER                          User’s branch within HKEY_USERS
       HKEY_CURRENT_CONFIG                        Hardware profile within HKEY_LOCAL_MACHINE\Config

                                              Figure 3 - Aliases on the Windows 9x registry.


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                                                                                The Registry

    registry menu within the editor. Hav-       this number can be varied by editing           In the case of NT, if the system is
    ing done so, you will be able to view       SCANREG.INI.                                configured for dual-booting you
    and edit the remote registry in the            Windows NT does not include a            should boot to DOS or Windows 9x
    same way as the local registry. When        specific registry backup tool. How-         before copying the registry files. Alter-
    you have finished, go back to the reg-      ever, the standard NT backup utility,       natively, boot to DOS from a startup
    istry menu and select Disconnect Net-       NTBACKUP.EXE, is able to back up            floppy. The files which you should
    work Registry.                              the registry, but only to supported tape    copy are those stored in the SYS-
                                                drives.                                     TEM32\CONFIG directory, which is
    Registry Backup                                                                         off the Windows directory. Note that
                                                Manual Backups                              you cannot use this method if the Win-
       Backing up the Windows registry              Another way of backing up the reg-      dows directory is on an NTFS parti-
    presents a specific problem: you can-       istry is simply to copy the relevant        tion, as the booted operating system
    not directly copy the relevant files        files. You cannot do this while Win-        will not be able to access it.
    while they are open, and they are al-       dows is running but, in the case of            Whatever the operating system,
    ways open while Windows is running.         Windows 9x, you can work round this         you can restore the registry by revers-
    However, there are a couple of tech-        either by booting to DOS (hold down         ing the above process.
    niques you can use to work round this.      F8 during startup, then select Com-
                                                mand Prompt Only) or by exiting to          Exporting The Registry
    Backup Utilities                            DOS from the Shut Down dialog.                   Another approach to backing up
        For Windows 95 users, the easiest           The two registry files, SYS-            the registry is to export it. Exporting
    approach is to use the Configuration        TEM.DAT and USER.DAT, are                   the registry is not the same as copying
    Backup utility (Figure 4). This copies      flagged as hidden, system and read-         it. Instead, the process creates a text file
    the registry to a compressed backup         only. Before copying them, you will         which contains the registry data in a
    file, the name of which is REG-             need to use the ATTRIB command to           format similar to that of an INI file (see
    BACKn.RBK, where n is a sequence            switch off these flags. Once that’s done,   Figure 5). If you need to restore the
    number. Up to nine generations of           you can copy the two files from the         registry, you can do so by re-importing
    backup can be made. You are                 Windows directory to another suitable       the text file.
    prompted to enter a description for the     location. Finally, use ATTRIB again to           An advantage of this approach is
    backup to help you subsequently iden-       restore the flags.                          that you do not have to export the en-
    tify it. The backup is always created in
    the Windows directory, but you are
    free to move it elsewhere.
        The same utility can be used to re-
    store and delete backups. It can only
    restore from the Windows directory
    so, if you have moved the file to an-
    other directory, you must move it back
    before running the utility.
        The Configuration Backup utility is
    not installed by default. You will find
    it on the Windows CD-ROM, in the
    \OTHER\MISC\CFGBACK                direc-
    tory. You can copy the two files
    (CFGBACK.EXE and a help file) from
    this directory to your hard disk, or you
    can run the executable directly from
    the CD-ROM.
        In Windows 98, the best way of
    backing up the registry is to use the
    Registry Checker (SCANREGW.EXE).
    This creates a backup automatically
    each time the computer starts, but it
    can also be run on demand. The
    backup is held in a CAB file, named
    RBn.CAB (where n is a sequence
    number), in the SYSBCKUP directory
    (this is a hidden directory off the Win-
    dows directory). By default, five gen-           Figure 4 - The Configuration Backup tool provides the simplest way of
    erations of backup are maintained, but                   backing up and restoring the registry in Windows 95.



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     tire registry. If you want to try out         Automatic Backups                             ple of extra benefits. As its name sug-
     changes which only affect one branch,             If the worst happens and you find         gests, it performs a check, albeit a rudi-
     you can limit the export to that branch.      yourself with a damaged registry and          mentary one, on the integrity of the
     Another benefit is that you can per-          no recent backup, there is an escape          registry. It does this at boot time. If it
     form both the export and import op-           route. As soon as Windows has suc-            detects a problem, it will automatically
     erations from within Windows.                 cessfully booted, it automatically cre-       restore the most recent backup. It will
         To start the export process, launch       ates a backup, which you can then use         also defragment the registry if it de-
     the Microsoft Registry Editor, select         to restore the registry if the need arises.   tects more than half a megabyte of
     the branch that you wish to copy,             This is not always an ideal solution, as      empty space.
     choose Export Registry File from the          you can only restore the registry as it           In the case of Windows 95, only one
     Registry menu, and specify the name           was at the start of the session, but it       generation of automatic backup is
     and location of the export file. Note         should be enough to get you out of            maintained. This consists of two files,
     that the Save dialog includes a choice        trouble.                                      named SYSTEM.DA0 and USER.DA0.
     between exporting the selected branch             In Windows 98, these automatic            They are hidden, system read-only
     and exporting “all”, that is, the whole       backups are held in the CAB files cre-        files in the Windows directory. If you
     registry.                                     ated by the Registry Checker. If you          need to restore from them, boot to
         The resulting file has the extension      need to restore from them, boot to            DOS, change the attributes (on the
     REG. You can view its contents by             DOS, then type SCANREG /RE-                   backup and the existing registry files),
     opening it in a text editor. When work-       STORE to launch the command-line              and copy the backups over the existing
     ing with this file, take care not to dou-     version of the utility. You will see a list   files. This will only work if you have
     ble-click on it, as this will re-import it.   of the available backups, from which          not booted to Windows since the reg-
     You can also import the REG file by           you can select the one you wish to            istry became corrupted.
     selecting Import Registry File from the       restore.
     Registry menu.                                    The Registry Checker offers a cou-        Registry Contents
                                                                                                    For the remainder of the article, I
                                                                                                 will describe the most important keys
                                                                                                 and values in the registry of a typical
                                                                                                 PC. As you read this, you might want
                                                                                                 to follow along by having your own
                                                                                                 registry open in the editor. For conven-
                                                                                                 ience, I’ll deal with the root keys in the
                                                                                                 order in which they appear in the edi-
                                                                                                 tor.
                                                                                                 HKEY_CLASSES_ROOT
                                                                                                    This branch is an alias for
                                                                                                 HKEY_LOCAL_MACHINE\Softwa-
                                                                                                 re\Classes (see below), and is a direct
                                                                                                 descendant of the REG.DAT file found
                                                                                                 in Windows 3.1. It is mainly used to
                                                                                                 keep track of file extensions and their
                                                                                                 associated applications, documents
                                                                                                 and OLE objects. It is a particularly
                                                                                                 large branch, with a very large number
                                                                                                 of sub-keys at the first level down (I
                                                                                                 counted over a thousand on my own
                                                                                                 PC).
                                                                                                    The first group of these first-level
                                                                                                 sub-keys have names that look like file
                                                                                                 extensions: .JPG, .XLS and the like.
                                                                                                 There is one of these for each “regis-
                                                                                                 tered” document type, that is, for each
                                                                                                 type of file listed in the File Types tab
                                                                                                 in the Options dialog in Windows Ex-
                                                                                                 plorer. As a minimum, the sub-key’s
                                                                                                 data contains a reference to the class
                                                                                                 definition associated with the docu-
                Figure 5 - You can export the registry to a text file, in INI format.            ment.



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                                                                                   The Registry

        The class definitions themselves are      certain installation routines to create a     tion and state of every toolbar and win-
    held in the remaining first-level sub-        history list for the control which            dow, a recently-used file list, the recent
    keys. These contain a descriptive name        prompts the user for the location of the      locations for opening and saving each
    for the document type (as it appears in       source files.                                 of the file types, and quite a lot more.
    the Type column in folder windows),               This is followed by Keyboard Lay-         This is an unusually large example -
    a pointer to the default icon and, where      out, which contains settings from the         most applications don’t store as much
    relevant, information about how the           Language tab in Keyboard Properties.          as this.
    application handles the documents as          It includes a key named Preload, which           Although         HKEY_CURRENT_-
    OLE objects and how the documents             in turn holds a key for each installed        USER\Software is mainly intended for
    are manipulated from the Windows              keyboard layout. These keys act as            third-party vendors, Microsoft also
    shell - for example, the actions avail-       pointers to keys within HKEY_LO-              has a presence there. The key includes
    able from the menu which appears              CAL_MACHINE\System\Curren                     sub-keys for each installed Microsoft
    when you right-click on the file.             t-ControlSet\Control\Keyboard Lay-            application (for example, HKEY_-
        Although HKEY_CLASSES_ROOT                outs, which in turn contain references        CURRENT_USER\Software\Micro-
    is updated automatically as applica-          to the keyboard drivers.                      soft\Office\8.0\PowerPoint) and also
    tions are installed and uninstalled,              The next first-level sub-key is Net-      for Windows itself (HKEY_CUR-
    there might be times when you need to         works. It in turn contains two keys:          RENT_USER\Software\Microsoft-
    edit it yourself. For example, you            Persistent lists the mapped drives            \Windows\CurrentVersion) . The lat-
    might want to restore a file association      which are configured for reconnection         ter holds user-specific settings for the
    which a new application has taken             at logon; Recent holds a key for each         Windows applets, Internet Explorer,
    over from an existing one. However,           share on a connected computer which           Task Manager and other components.
    rather than editing the registry di-          has been accessed from this computer.            In Windows NT, there are some ad-
    rectly, it is easier and safer to make this   In each case, this shows the connection       ditional first-level keys below
    type of change from the File Types tab        type and provider name.                       HKEY_CURRENT_USER. They in-
    in the Options dialog.                            Next, the RemoteAccess sub-key            clude Console (settings for the Com-
                                                  contains details of the user’s Dial-Up        mand Prompt window), Environment
    HKEY_CURRENT_USER                             Networking connections. The key it-           (environment variables read at logon)
        This root key contains information        self contains settings common to all          and Unicode (references to applica-
    specific to the user, and is an alias for     connections, such as the area code and        tions that support Unicode).
    the user’s branch within HKEY_US-             the number of redial attempts. Below
    ERS (described below). If user profiles       this, the Addresses and Profile keys          HKEY_LOCAL_MACHINE
    are enabled, it relates to the user who       contains settings for specific connec-            This is another large root key. It is
    is currently logged on. The key con-          tions.                                        the home of all the computer-specific
    tains seven first-level sub-keys.                 The last of the first-level sub-keys in   information, including details of the
        The first of the first-level sub-keys     HKEY_CURRENT_USER is easily the               hardware configuration and any ma-
    is named AppEvents, and contains de-          largest. It is named Software, and it is      chine-specific settings for the installed
    tails of the sounds which the user has        one of the two parts of the registry          applications. Whereas each user who
    associated with system or application         specifically intended for use by appli-       logs onto the PC sees different settings
    events. It is organised into two subsidi-     cations (the other is also named Soft-        in HKEY_CURRENT_USER, they all
    ary keys: EventLabels contains the            ware, and is in HKEY_LOCAL-                   see the same information in
    names of the events, and Schemes con-         _MACHINE).                                    HKEY_LOCAL_MACHINE. It con-
    tains references to the corresponding             Immediately below HKEY_CUR-               tains seven first-level sub-keys.
    sound files. Schemes is itself organised      RENT_USER\Software, there is a key                The first of the first-level sub-keys,
    by application, and for each event            for each vendor which has applica-            named Config, contains all the hard-
    within the application there is a cur-        tions installed on the computer. This in      ware profiles which have been set up
    rent and a default setting.                   turn contains a key for each of the ven-      for the machine (do not confuse these
        The second of the first-level sub-        dor’s installed applications and, in          with user profiles, which are in
    keys is named Control Panel. This con-        some cases, a further sub-key for each        HKEY_USERS). Each hardware pro-
    tains the settings that used to be made       installed version of the application. Be-     file has its own key, one level down
    from Control Panel in Windows 3.1:            yond that, the content of each key is for     from HKEY_LOCAL_MACHINE\-
    colour schemes, screen savers, wallpa-        the vendor to decide. Typically, they         Config; these are named 0001, 0002,
    per, keyboard repeat rate, mouse              contain user preferences, histories and       etc. Each profile contains configura-
    speed and so on. These settings are           the like.                                     tion details for the monitor, printers
    spread over a number of subsidiary                As an example, my own registry            and other devices present in the pro-
    keys, each of which roughly corre-            includes a key named HKEY_CUR-                file, as well as certain Internet-related
    sponds to one of the old Control Panel        RENT_USER\Software\JASC\Paint-                settings.
    modules.                                      Shop Pro 5, which in turn contains 43             The second of the first-level sub-
        The next first-level sub-key is called    sub-keys. As well as my preferences           keys is Enum. This holds information
    InstalledLocationsMRU. It is used by          for PaintShop Pro, these store the posi-      about all the devices and peripherals



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     installed in the computer, including          HKEY_LOCAL_MACHINE is named                  identical to HKEY_LOCAL_MA-
     such details as the device type, drive        System. It contains a single key (in         CHINE\Config\nnnn, where nnnn is
     letter, hardware ID and manufacturer.         Windows 9x), named CurrentControl-           the profile number.
     It might also include devices that are        Set, which in turn contains two keys:            In Windows NT, hardware profiles
     not currently available. For example, if      Control and Services. The former             are stored in HKEY_LOCAL_MA-
     you have changed your monitor, both           stores certain information needed at         CHINE\System\CurrentControlSet-
     monitors might have an entry (in              boot time, including the computer            \Hardware Profiles, and HKEY_CUR-
     HKEY_LOCAL_MACHINE\Enum\-                     name, file system settings, multimedia       RENT_CONFIG is an alias for
     Monitor), with a further entry, named         resources, descriptions of network           HKEY_LOCAL_MACHINE\System-
     Default_Monitor, used to point to the         providers and information about na-          \CurrentControlSet\Hardware Pro-
     one currently installed.                      tional language support. The Services        files\Current.
         Enum contains a key for each class        key lists the device drivers which Win-
     of hardware. These vary according to          dows must load during booting.               HKEY_DYN_DATA
     the installed devices, but will typically         In Windows NT, HKEY_LO-                     This final root key (which is not
     include: BIOS (devices used with a            CAL_MACHINE does not have Con-               present in NT) is a memory-resident
     plug-and-play BIOS), ESDI (installed          fig, Enum or Network sub-keys; some          copy of certain other registry items. It
     ESDI drives), Flop (floppy disk drives),      of their settings can be found under the     contains information which Windows
     LptEnum (plug-and-play printers),             System key instead. The Hardware key         needs to retrieve particularly quickly.
     MF (multi-function boards), Monitor           contains more extensive information             The root key contains two sub-keys.
     (monitors), Network (network proto-           about hardware devices and their cur-        The first, named Config Manager,
     cols and bindings), PCI (PCI devices),        rent status (roughly corresponding to        holds details of the current hardware
     Root (certain legacy devices), SCSI           the details shown in the Windows NT          configuration as seen by the Plug-and-
     (SCSI devices) and SerEnum (serial            Diagnostics applet). The Security key        Play Configuration Manager. Win-
     plug-and-play devices).                       is also more extensive; it contains the      dows builds this information (which is
         The next first-level sub-key, named       settings which are configured from           sometimes referred to as the hardware
     Hardware, contains a few details about        User Manager. And there is one addi-         tree) by examining the hardware dur-
     the CPU, floating-point processor and         tional first-level key in NT: the SAM        ing booting; the information is then
     serial ports. This is followed by Net-        key holds user and group account in-         updated dynamically as plug-and-
     work, which stores information about          formation.                                   play devices are installed and re-
     the current network logon (if any), in-                                                    moved.
     cluding the user name and the name of         HKEY_USERS                                      The other sub-key is named
     the primary network provider. Next,               This root key contains a sub-key for     PerfStats. This contains performance
     the Security sub-key contains details of      each user profile. There is a further        information about network compo-
     any security provider.                        sub-key, named .Default, which pro-          nents.
         The largest of the first-level sub-       vides default values for new user pro-
     keys comes next. It is named Software,        files. If user profiles are not enabled,
     and it closely parallels the Software         .Default stores the settings for the ac-      New Report: "The 16
     key in HKEY_CURRENT_USER.                     tual user.                                    Best-ever Freeware Utilities"
     However,         while       HKEY_CUR-            When a user logs on, Windows cre-
     RENT_USER\Software contains user-             ates the HKEY_CURRENT_USER                    Click here to get it for free
     related settings for the installed            alias from the corresponding profile.
     applications, the HKEY_LOCAL_MA-              The contents of the profile key within
     CHINE version contains computer-              HKEY_USER are therefore identical to
                                                                                                                             PCSA
     specific settings. For example,               that of HKEY_CURRENT_USER (de-
     HKEY_CURRENT_USER\Software\-                  scribed above).
     Microsoft\Office\8.0\PowerPoint in-
     cludes the current user’s preferences         HKEY_CURRENT_CONFIG
     for PowerPoint; the corresponding                 As mentioned earlier, HKEY_LO-
     branch in HKEY_LOCAL_MACHINE                  CAL_MACHINE\Config contains de-
     contains the application’s directories,       tails of the installed hardware profiles
     details of the installed filters and so on.   (this applies only to Windows 9x).
         In addition, HKEY_LOCAL_MA-               Each profile has its own key within
     CHINE\Software includes a key                 Config - named 0001, 0002 etc - which                  The Author
     named Classes, which holds informa-           holds configuration details for the pro-       Mike Lewis is a freelance technical
     tion about registered file types and          file. There is always at least one profile     journalist and a regular contribu-
     their associated applications. This key       key.                                           tor to PCSA. You can contact him
     is aliased by HKEY_CLASSES_ROOT,                  The HKEY_CURRENT_CONFIG                    by email at mike.lewis@itp-jour-
     which is described above.                     root key is an alias for the current hard-     nals.com.
         The last of the first-level sub-keys in   ware profile. Its content is therefore



File: E1209.6
                                                   PC Support Advisor                                        Update 127 (May 1999) Page 10
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