As mentioned a while ago, I use Diskeeper 2008 pro for defragging. Unlike the other programs in the thread, it isn’t free, but it’s got features that are exceptionally useful for me like auto defrag (I enable it for 4 drives lol), system files defrag, low resource usage etc.
I recall I tried defragller when it was in beta. Froze on me a couple of times (but no harm done) so I uninstalled it. Haven’t tried the newer versions.