Since many performance problems in Windows XP and Vista can be traced to a particular program, you may need to enter Safe Mode (which runs only essential programs) to diagnose the problem or remove a recalcitrant application. To see instructions for accessing Safe Mode in XP, http://pcsupport.about.com/od/fixtheproblem/ss/safemodexp.htm
For instructions to do the same in Vista, http://www.bleepingcomputer.com/tutorials/tutorial61.html#vista
Another common troubleshooting technique is to use System Restore, which, as you might guess, restores your system configuration to a given point. It doesn't affect your actual files, but if you're concerned about losing data it wouldn't be a bad idea to back up those files first. There's a walkthrough here http://support.microsoft.com/kb/306084 for WinXP, and here http://www.bleepingcomputer.com/tutorials/tutorial143.html for vista
Posted by dmcheckers
Windows 7 also is equipped with a system restore and a safe mode. This is how you enter Window's 7 safe mode
http://windows.microsoft.com/en-US/windows-vista/Start-your-computer-in-safe-mode
And this is how you can use system restore
http://windows.microsoft.com/en-US/windows7/What-is-System-Restore

