"Neither UNTFS.DLL nor UFAT.DLL call file system drivers to take any
part in a format or chkdsk operation - they directly read and write raw clusters on the drive."
That's why you have to unmount the drive when ie. formatting or chkdsk'ing it. Defragmentation however can be done whithout unmounting, because the fs driver handles this job. The IOCTLs are documented in the platform sdk, defragmentation really doesn't work using fmifs/ufat/untfs/u...
- Thomas