Slap in a 2nd hard drive and then backup all your stuff to it. Then format your main drive an do a fresh install of windows xp. Depending on what XP cd you have, there is a facility to do a simple repair on the installation which may help.

IMO, wipe it clean and start again. If you've got corrupted data, there is a chance your personal stuff could be corrupted, and moving it across won't make much differance.