Many Spyware, Trojan Horse Virus will load into your computer memory right after the computer starts. Sometimes, you need to start computer in Safe Mode to remove those Spyware, Trojan Horse, Web Search Toolbars, Advertisement Popup malicious programs.
The simple way to start computer into Safe mode is to press the F8 key while booting the system.
To start Windows XP in Safe mode
To start Windows 2000 in Safe mode
After you are in the Safe Mode, then you can clean up the settings of Startup programs by running MSCONFIG, uninstall program you don't need from the Control Panel and run anti-Virus Program or remove Virus.