http://www.raxco.com/
Over the years i've tried a few other various deframenters for HD's, and always seem to come back to Perfectdisk. Why? Because of its interface and.. it just plain works well. Fast too. This is an excellent company and it shows.
I just did another defrag a few days ago using PD 8.0, and i'm still impressed. System ws defintiely improved and faster upon defrag. Try it out free and see if ya like it.