The fastest way to defragment your hard drive
review from ClifNotes, Apr 2007, permalink Disk Cleanup
I haven't tried this yet, but I will when I get time. If you try it, be sure to tell us in a comment below.
Quote from the website
The never-ending two-step defragmenting process of Vista can soon become a thing of the past. With certain tools, we were able to cut defragmentation time of 25 GBs of files with Vista Ultimate from 82 minutes to 6 minutes!!! That is defragmenting 10X faster than the built-in Vista defragmenter! The tutorial also works with Windows 2000 and XP.
http://vistarewired.com/2007/02/15/defragment/