If you are wiping the free space on a drive (in this case, a spare platter drive for large data amounts), but then cancel it before it completes, the entire drive becomes unreadable by Win7 and asks for a format. Under Disk Management, the file system type of the drive is reported as "RAW". Other software can be used to recover the contents of the disk (the non-free space data, the data which you wanted to keep), but obviously CCleaner shouldn't have created this situation in the first place.
Again, the problem seems to arise when cancelling a "Wipe Free Space" (1 pass) procedure. It was about 90% finished.
