Please run the following:
Go Start and then to Run,
Type in: sfc /scannow
Click OK.
Have Windows CD/DVD handy.
If System File Checker (sfc) finds any errors, it may ask you for the CD/DVD.
If sfc does not find any errors in Windows XP, it will simply quit, without any message.
If you don't have Windows CD....
Go Start and then Run
type in regedit and click OK
Navigate to the following key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup
On the right hand side, find: SourcePath
It probably has an entry pointing to your CD-ROM drive, usually D and that is why it is asking for the XP CD.
All we need to do is change it to: C:
Now, double click the SourcePath setting and a new box will pop up.
Change the drive letter from your CD drive to your root drive, usually C:
Close Registry Editor.
Now restart your computer and try sfc /scannow again!
After the first run, reboot your computer. Do a second run. Now the scan and fix is finished.