I suppose the first question would be do you know of anything that might have caused the problem?
Have you run an anti-virus checker?
What does Disk Management show about your drives?
It might be advantageous to open an Administrative command prompt and type SFC /scannow to check your system files. Give it some time and let us know if show nonrecoverable file errors.
If something is going on with your hard drives, running Chkdsk might help clear up the problem. There are several switches you can use with it, but I would suggest you first do a check and not a repair to see what it might show. Your next step might depend on what type of errors were found, if any. So, if the partition with the problem was d: you would use chkdsk d: then later, to fix problems, if you choose, add a /F to the end (chkdsk d: /f).
Do you see any indications of disk repair activity in the Event Viewer? Not sure what it might be called.
If you have the Administrative command prompt window open, you can type fsutil repair query d: to see if the drive is set to self-healing, and once again, the drive letter may be different for you.
