I analyzed a 150 GB drive (109 GB used). It had already been partially defragged, 9 files fragmented with 29 fragments. I come back 20 hours later, it's at 55% and still going. I can see the file names passing by on the display, after awhile I notice that it's the same exact files over and over. I stop the defrag and re-analyze. There are now over 1200 fragmented files and many thousand fragments... I defragged again with Defraggler only this time "manually" by defragging files in the file list and 'defrag free space', I repeated until the drive was mostly defragged, this seemed to work OK and it did not get stuck in a loop.
The 'defrag loop' problem happens on all my large drives (over 100 GB) on all my machines. The older versions of Defraggler did not have this problem (just before the command line defraggler came out, I don't recall the version #).
OS: XP Pro 32bit SP3
4GB RAM (3.5 GB effective)
Rick