If you have the XP CD.
boot from it
How to:
Insert the Windows XP CD-ROM into the CD-ROM drive, and then restart the computer.
Click to select any options that are required to start the computer from the CD-ROM drive if you are prompted to do so.
When the "Welcome to Setup" screen appears, press R to start the Recovery Console.
When you are prompted to do so, type the Administrator password. If the administrator password is blank, just press ENTER.
In recovery console , do:
chkdsk /r
(this can take some minutes)
exit
(exits the recovery console and reboot the pc)