Boot into Safe Mode:
Tap F8 as the machine is polling the A drive.
Then, run SCANNOW, using your XP CD:
The following assumes you have an actual XP CD as opposed to a restore CD or
restore partition supplied by your PC manufacturer.
Go to Start, type sfc /scannow in the run box and press enter. Note, there
is a space between sfc and the forward slash. You will be asked for your XP
CD. Be aware, upon inserting the CD the XP setup screen may appear, this is
not a part of sfc /scannow, rather it is being invoked by autorun. Simply
minimize the screen and allow sfc to continue.
-Michael Soloman