windows 98 drivers are different to xps, so either way he has to reinstall xp drivers. Also 98 drivers could conflict with whats on the system and he could loose and data.
I say at the boot up hit f8 and run in safe mode and run diagnostics and that should find the software glitch also check what software you have downloaded it maybe something has messed up ur system like a virus or sum one may have hacked it.