We often recommend defragmenting your hard drive(s) to stop data loss and maintain high performance.
Diskeeper offers several advantages over the standard Windows program. It can run if there are other applications open and offers much more information about the state of the hard drive and the effect of the defragmentation.
Other features include defragmenting before Windows has started up, so that it can fix the files that cannot be touched when Windows is running.
It also has a Smart Scheduling feature, where Diskeeper automatically defragments the hard drive as and when it sees fit, leaving you to get on with doing your work.
The new 2007 edition contains a feature called InvisiTasking, a technology which will enable a system maintenance task to run invisibly in the background. Essentially automatic background defragmentation.