Did you try tapping F8 at start up to get into the boot menu ?
If that doesn`t work,boot into the XP CD and run CHKDSK /R
from the Recovery Console.
To get the CD to boot,you have to make the CD/DVD drive
the first boot device in the BIOS.Tap del or F1 or F2 immediately
after pwer on.There are variations on those keys,so google if they
don`t work.