This is an old DOS routine:
C
chkdsk /f or C
chkdsk d: /f where d: is a drive other than the default.
simple as that. You can do this in a Command window.
Got me out of a deep, deep hole as recently as last week when Partition Magic aborted in the middle of an operation (operator error!) and one of my FATs was corrupted.
I held my breath while restoring access to over 20GB of video data. All backed up, of course, but, Oh!, what a long job to recover the situation.
Chkdsk repaired the second FAT