Under Windows XP, what are some alternatives to the default disk defragmenter?
Defraggler from the same guys who brought you CCleaner and Recuva! All are great pieces of software.
JKdefrag is what I have been using to great effect. It's also Free!
PerfectDisk is one that actually works and is not totally annoying. :)
DisKeeper is good.. has a managed version for enterprise. http://www.diskeeper.com/
It will actually move files around (instead of just defragging individual files). In this way files that are in the same folder will all be physically be close on the disk.
It can also defrag files that are in use by Windows (e.g. the MFT) by doing defragging at boot time. This however requires that the defragging runs as a result of being defined in a job.
I can recommend it. I have used it for many years without any problems and it is not intrusive; there is no noticeable degradation in performance while it runs.