I agree. This is actually a great chance to learn a lot. As the above poster recommended, use a Knoppix disc to check out the hard drive and see what's there. If I were you, I'd use that as an opportunity to back up any important files that may still be on the computer.
Once you're all backed up, you really could have a lot of fun - especially if you think you're going to have to reformat and start over with Win XP anyway!
For example, you could grab a Linux disc and try installing a brand new distro to your drive (they run a lot better than live discs), play with it for a day, and delete it. You might see something you like and decide to dual boot one day. Hey, if you're going to have to reformat your drive and start fresh, have fun first (and learn a bit, too, at the same time)!