Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation. A virus might corrupt or delete data on your computer, use your e-mail program to spread itself to other computers, or even erase everything on your hard disk.
As soon as you suspect that your computer has a virus, remove your computer from any networks it might be on, as well as from the Internet, so that you don't inadvertently spread the bug to others. Unplug your network cable if you have to.If you have virus-scanning (anti-virus) software installed, run it. If you don't have anti-virus software, you'll need to obtain some.
Turn off system restore because this is where most of the viruses hide. Anti-virus programs can eradicate the virus in this zone unless system restore is turned off. To find this in Windows XP, right click on "my computer" then click on "properties" then choose "system restore" then tick the "turn off system restore" button. Run the anti-virus software then turn system restore on again.Follow the instructions that came with the anti-virus software. Keep running the virus-scanning software until your computer comes up clean.
Reconnect your computer to the Internet and check with the anti-virus software's publisher to make sure you have the latest updates. If not, download them now. After updating the anti-virus software, run it again until your computer comes up clean.
Sometimes viruses are very persistent meaning that if you kill it, it restarts itself automatically. If this happens, it is important to know where the program is located on your hard-drive. For this, I recommend Process Explorer. It is free, and works on all Windows OSes.
Run Process Explorer, and find out where the file is. If you aren't sure about which process is the malware, right click every one you know isn't bad, and click "Google Search" and that should tell you if it is bad. Once you know which and where the bad file is, reboot and tap F8 while booting. When you see the option, tell your computer to boot to safe-mode. This will run only the basic, necessary-to-run-your-computer programs. Then, go and delete the file that you have found to be malware. Do the registry check mentioned above, and boot normally. If you do not know how to access your registry, it is Start->Run->regedit in Windows XP, and probably older ones, but I can't guarantee that. Beware! The registry is highly sensitive! Don't play with it, because that could ruin your computer!
If you are searching the Internet for anti-spy-ware/virus programs, you should be wary. Some of them call themselves the anti of what they really are. Anything that says immediately that your computer has many problems (100s to 1000s) should not be trusted. Don't be scared into buying it, because that's exactly what the makers want; and if you're like me, you would agree that anyone who has to lie to scare you into buying from them doesn't deserve your money.