Hi
Did this problem occur after a XP reinstall?
Or did drive come from another system with latter windows?
Why are you using exFat?
Is there any data on it?
Internal or external drive ?
If you can extract data on another PC
Repartition and format as NTFS unless very good reason
A gparted live Linux cd image may be able to read the disk and check it is working not damaged
http://gparted.org/features.php
Regards
Mike Barnes