XP does not have SATA drivers native to it.

If you have a XP cd with SP3 included, F6 the drivers in and remember with XP, you have to use a floppy.
Then do a repair install.

I would suggest, jumping the hdd into a computer/ USB enclosure/ etc., salvage what you hate to lose and do a clean install to a hdd, And up date to Win 7 while as XP only has about 3 - 4 months left of support.