Hi Kempus,
Can you boot into safemode? (See
here for info on how to, if needed.) If so, run your virus checker. If you don't have one, then and go
here, and run the online virus scan; choosing the
Autoclean option just before clicking the
Scan button. (You can access the 'net in safe mode with XP.) Then reboot back into normal mode if you can.
Let me know how you get on.
Cheers
Liam