Yes, Disk Defrag will defragment any fragmented file on your drive, but it will not optimize that drive. That is, it leaves all of the files scattered about your drive, so that you can still have your free space cut up into 1,000's of bits and pieces. That's what happened to me, and as a result, I could not defragment my Virtual PC disk image file, because it would not fit into one of the many small free spaces on the drive, even though I had twice the total space needed.

Bottom line: Disk Defrag resolves only half of the problem of disk fragmentation: in my case, the worst of the two problems.

Finally, there is only a single progress bar showing the amount of defragmentation. There is no interactive display of the blocks being moved around like there is in other defragmentation tools (or even in the free Windoze defragmenter).