I myself have been wondering about 3rd party defragmenters and if they really work...I have seen many threads from others with the same questions I had... Recently I stumbled upon an online pdf version of MaximumPc online and started reading the PDF version... They actually have a section where they tested "PerfectDisk" , Diskeeper, and Auslogics against the Built in Defrag of Vista.. Looks like none of them made any increase in performance and actually slowed down the PC... Here is the link to the PDF version...The article starts on page 36... Let me know what you guys think.....
dl.maximumpc.com/Archives/MPC0608-web.pdf
dl.maximumpc.com/Archives/MPC0608-web.pdf