You can try running the chkdsk /r command...from the Recovery Console on the XP CD.
Ensure that the system is set to boot from the optical drive.
Insert the Windows XP CD into your CD drive and restart your computer. If prompted, select any options required to start (boot) from the CD.
When the text-based part of Setup begins, follow the prompts. Select the repair option by pressing R
Type 1 (for the XP install) and hit Enter.
At the password prompt, just hit Enter.
Type chkdsk /r (exactly as I have) and hit Enter.
Upon completion of the command...the system will reboot.