PC World
"Defraggler will show you all your fragmented files. You can click one to see where on the disk its various pieces lie, or defragment just that one. This can be useful when dealing with very large, performance critical files such as databases... Piriform Defraggler is free, fast, marginally more interesting to watch than the default, and has useful additional features. What's not to like?"

Read the full review at:
http://www.pcworld.com/downloads/file/fid,72958/description.html