Urgent Computer Restoration Help?

I don't really know what caused the problem, one day my computer's working fine and today it's gone to hell in a hand basket. It's all sorts of screwed up and I've tried everything short of calling the geek squad. I've decided to just start fresh and restore it but the thing is the only disk this computer(windows 7) came with is a Kaspersky Anti Virus Installation CD. I've never had reason to do this with any of my previous computers so I don't have much knowledge on the subject, help?