one is to go:
my computer, rclick on the offending drive (usually C:\)
properties-tools-check my disk for problems
tick both boxes, hit OK.
it should say it will do it on a reboot... hit okokok.
reboot, go make a coffee.
If that no go, then something is wrong with chkdsk.
hmmm.
The same thing can be achieved by running the guided help thingee by microsoft, here:
http://support.microsoft.com/kb/315265
If that is the case, then Tere be Drakons inst thy PC...
so BACK EVERYTHING UP!!!! NOW.
there is a good tutorial on this proceedure, plus making a bootable floppy for the job (you might be able to do this with a CD if you understand the command line they have used.) and also how to do it using a genuine winXP install disk+ recovery console.
http://pcworld.about.com/magazine/2111p196id112479.htm
hope it helps...