Power Defragmenter is based on the free contig defragmentation tool developed by the guys at sysinternals. “ Contig is a single-file defragmenter that attempts to make files contiguous on disk. Its perfect for quickly optimizing files that are continuously becoming fragmented, or that you want to ensure are in as few fragments as possible. “

For me this is much better than the windows built-in defragmentation tool. Power Defragmenter has a simple, straight-forward GUI with easy options. You can choose from four defragmentation options:

1) Defragment Files
2) Defragment Folders
3) Defragment Disks
4) Powermode Disk Fragmentation

The last option defragments the files and than tidy up the drive for optimum performance.

Power Defrag in action:

Download Power Defragmenter GUI 2.0.125:
http://www.majorgeeks.com/Power_Defragmenter_GUI_d4647.html

Download Contig by itself from sysinternals:
http://technet.microsoft.com/en-us/sysinternals/bb897428.aspx