?A computer virus is a small software program that hampers the performance of your computer. It can be easily spread from one computer to another. It may corrupt or erase data on your PC, can delete everything on the hard drive and use an e- mail program to spread the virus to other computers. Computer viruses are most easily transmit by attachments in e- mail messages. Therefore, it is recommended never to open an e- mail attachment unless you are sure who actually sent the message. They can be disguised as attachments of funny images, greeting cards, or audio and video files. Computer viruses can also spread by using downloads on the Internet. They can also be concealed in pirated software or in other files that you may download. You can face the following problems if your PC is infected with computer virus: Windows would not start even though any system changes are not made by you or you have not installed or removed any programs. If there is repeated modem activity. If you have an external modem, and notice frequent light blinking even when you are not using the modem. You may be unexpectedly supplying pirated software. Windows does not initiate because certain significant files are missing. Additionally, an error message might be received by you that lists the missing files. The computer sometimes stops responding before the desktop icons and the taskbar appear. The computer is running very slow or it takes longer than expected time to boot. Even though your PC has sufficient memory, you receive an o ut-of- memory error messages. Programs are installed mistakenly. Windows restart unexpectedly. A disk utility such as Scandisk reports several disk errors. A partition vanishes. You cannot initiate Windows Task manager. Antivirus software shows that a computer is infected with a computer virus. Note: These problems may occur due to problems in Windows that are not caused by a computer virus. Your computer against viruses can also be protected by using a secure Internet connection and by combining it with a firewall which is not difficult to install. You can take the benefit of antivirus software and updates provided by your network, along with the firewall. To protect your computer against viruses, follow the given steps: Turn on the firewall on the computer Keep the computer system up-to-date. Use updated antivirus software on the computer. Use updated antispyware software on the computer. About Author: I am tech support specialist for iYogi, a leading IT support based in India, iYogi provides pc support services via phone and remote access for home users and small businesses worldwide. To install antivirus software visit iYogi.net or call on 800-237-3901 .