Reinstall Windows

If you do not have a recovery DVD, do not worry, it is not difficult to install windows. Just follow the appropriate procedure from this website: http://www.windowsreinstall.com/ If you have a problem finding the right procedure, post it here.

A more detailed XP reinstall procedure:
http://www.wikihow.com/Install-Windows-XP

A more detailed Vista reinstall procedure:
http://www.wikihow.com/Install-Windows-Vista

Another advantage of reinstalling windows is that if you still have the same problem after reinstalling, at least you have eliminated many if not most windows software problems. This can be crucial to determine a hardware problem. It will also give extra info and extra motivation to your computer store to search for a hardware problem.

Youtube video's:

How to install Windows XP:

How to Format and Reinstall Windows xp: