|how do you reset your password|
This is very easy to do, but rather than explain it all here, I've found two articles that show you exactly how to do it.
This is the easiest method, but for this you need to have the Windows Setup DVD that came with you computer, if not go to the second link.
If you dont have the setup DVDs, then follow this link to fix it. These methods requires a bit more work though, but is just as effective.
How to login Windows xp when I forgot my password