Why a 3rd party one? The built-in one actually isn't all that bad as defraggers go.

Slightly OT, why bother defragging? I've never found the performance benefit to be worthwhile. Then again, I reinstall more frequently than most and keep 30-50% free space on my HD, so that probably helps. But defragging was more of an issue when seek times were way slower and drives generally had lower performance metrics. I don't think it is nearly as significant an issue these days.