Check out
this thread. The subject is discussed there.
With hard drives getting larger and larger a lot more attention is being paid to defrag programs. there's an article somewhere here on Toms about this very subject , I was unable to quickly find it but you may want to search for it.
If I remember correctly the article I am referring to compared windows Defrag to another commercial defrag program which I can't remember at the moment. I do remember the results of the comparison and it was concluded that there wasn't very much difference between the two.
Want to get rich? come up with a faster way to defrag these large hard drives.
P. S. This article should have been in the hardware section under hard drives.