I've seen this happen before. Sometimes, when you first install XP on your PC, you are prompted for an Administrator password. Once you get into windows, you make an administrator account, but it is your name. Odds are you'll forget your originial admin password. I think there's a password cracker out there that might be able to help, but I don't know it off hand.
What I had to do in this situation is slave the hard drive in another PC and then just fdisk it. It wasn't fun, and this won't apply with your laptop. Oops.
*\'Failure\' is not a four-letter word.