you can still set the system back to before the problem started with system restore, or you can repair install the operating system if you have the XP operating system disk. Do the restore first.
Both of these options do not erase your personal files. Repair install needs to reload the system drivers, from your driver disk or from the manufacturer''s website.
In any case before you try one or both, back up all your personal files to CD, DVD, or an online backup service.