Ok, but I have further info. After running Defraggler five consecutive times and only getting the fragmented files down to 21%, I ran the Disk Defragmenter from 'System Tools' and got 0% as I stated originally. Then, after posting my original question I ran Defraggler again and this time got 0% fragmented files with zero fragments as well. In reference to your response, I accept that Defraggler considers more files than the Disk Defragmenter but why would Defraggler also give me 0% fragmentation after running Disk Defragmenter when before it was 21%? Wouldn't those "not defraggable" files remain untouched if they are not counted by Disk Defragmenter? Doesn't this suggest that Disk Defragmenter may be better than Defraggler at defragmenting files? After all, running Defraggler five times still gave me 21% fragmentation while after running the Disk Defragmenter from 'System Tools' once, the fragmentation went down to zero, and this is according to Defraggler, itself.