You may have to re-install windows. If you have an actual Windows XP cd there is an option to leave the drive alone, meaning you won't lose your data. If you only have a restore disk, you are liable to lose information unless you back it first.
There is a repair function in the Windows XP setup, however not very user friendly.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>
Overclocking Results: <A HREF="http://Mr5oh.tripod.com/pc2.html" target="_new">http://Mr5oh.tripod.com/pc2.html</A>