Not a very helpful error, is it?
You probably have disk errors that need to be repaired first. Go to Windows Explorer, right click on the Drive and select Properties, then Tools and error checking. Let the error checking run at reboot if it prompts for this. Reboot the PC, let the scan complete and then try a Defrag manually from Start/All Programs/Acessories/System Tools/Disk Defragmenter
-steve