Start and then to Run
Type in Chkdsk /r Note the space between k and /
Click Enter ...It will probably ask if you want to do this on the next reboot...click Y
If the window doesn't shutdown on its own then reboot the system manually. On reboot the system will start the chkdsk operation
This one will take longer then chkdsk /f
Note... there are 5 stages...
It may appear to hang at a certain percent for a hour or more or even back up and go over the same area...this is normal...
DO NOT SHUT YOUR COMPUTER DOWN WHILE CHKDSK IS RUNNING OR YOU CAN HAVE SEVERE PROBLEMS
This can take several hours to complete.
When completed it will boot the system back into windows.
Let me know if this fixes the problem
Once this is done and if no improvement then follow the next steps.
Go Start and then to Run ("Start Search" in Vista),
Type in: sfc /scannow
Click OK (Enter in Vista).
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.
In Vista you will receive the following message: "Windows resource protection did not find any integrity violations".
For Vista users ONLY: Navigate to C:\Windows\Logs\CBS folder. You'll see CBS.log file.
Usually, it's pretty big file, so upload it to Flyupload, and post download link.
If you don't have Windows CD....
This applies mostly to Windows XP, since Vista rarely requires use of its DVD while running "sfc"
Note This method will not necessarily work as well, as when using Windows CD, because not always ALL system files are backed up on your hard drive. Also, backed up files may be corrupted as well.
Go Start and then Run
type in regedit and click OK
Navigate to the following key:
You will see various entries Values on the right hand side.
The one we want is called: 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 SourcePatch 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!
Thanks to Broni for the instructions