|Clarify something. Are you stating you now have two instances of WinXP installed on your laptop and you didn't install the second one?|
Are you sure this wasn't done while someone had physical access to the laptop?
Have you ever given anyone remote access to your computer?
Do you have a strong password on your wireless network?
Do you use any security measures on the laptop? Like log-in passwords for instance?
Run your AV and also malwarebytes.