Hi Ed, You need to look around in the forums using "search". type 5400 or UDMA to get results. I can't remember right off where I went for detail info, but the info was that the new 66 UDMA and 100 UDMA works if you have a 7200 rpm drive. Otherwise there is no advantage over 5400. Go the the link below and search using 5400 as target. Several discussions on the differences. http://sysopt.earthweb.com/find/ssmain.cgi?results=0&query=5400+rpm God Bless, and have fun. _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com Visit our website regularly for FAQs, articles, how-to's, tech tips and much more http://freepctech.com