Well, I have a fake version of Windows XP Pro with SP2, so I can't use some programs. I've tried to reinstall XP with my original CD but when the computer boots up, it won't even notice that the CD is in the drive. Not sure what the problem is so I can't really say much more. I'd really appreciate any advice, please and thank you to everyone that helps.

Oh yeah, I've tried installing it while the computer is still on, but when I click on the install button(the 1st one), it tells me that the version of my CD is older than the one that is installed on my computer so it doesn't allow me to install. Other than that, that's all I can say about the problem.