I use PerfectDisk and I defrag several times a week.

Perfect Disk. And I follow a strict ritual: chkdsk, pagedefrag (www.sysinternals.com) and offline and defrag as often as possible. Had my shares of destroyed disks in my career...Diskeeper: keep away of this, algorithms are bad, it probably destroys parts of the $Bitmap entries (irrecoverable problem) and yields no performance over Perfect Disk but is much more complicated and overbloated. Made the biggest troubles on 2 independent systems, esp. after uninstalling.UltimateDefrag: the version I had at the beginning of the year was unable to cope with files > 1 GB, never got the layout done (terminated way too soon disrespecting my settings) and I never saw it do anything during offline defrag.OO defrag: tested 2 times, and each time it destroyed my RAID completely. Seems it's for single disks only...BTW: the defragger that comes with Windows is simply crap, I guess even the simplest freeware replacement is better than this thing.Andreas