PC Review have just released a review of Diskeeper 2007, an advanced hard disk defragmentation application

The question still remains whether defragmentation actually improves disk performance though. My own experience is that it does. Having said that, I had to let my hard disk fragment for at least six months before I actually noticed any lack of performance. De-fragging did actually put a 'sparkle' back into my system. And if Microsoft didn't consider defragmentation to be a desired thing they wouldn't have included the function within Windows. And whilst I've mentioned Windows, it's worth noting that Diskeeper will defrag your drives in a fraction of the time Microsoft's built-in software takes to do it.

Diskeeper 2007 Review