For a free defragmenter, I heard good things about this one:
http://www.auslogics.com/) but I haven't tried it yet.
Thank you. It looks quite pretty:
http://img.photobucket.com/albums/v170/tk102/9252db10.jpg)
and it gives a good report of what files it defragged, which files didn't have enough space to defrag, and which files were unmovable. Unfortunately it runs in Windows, which gives rise to that last category. :) Still, it seems much better than the default utility.