I have used both Windows Defrag, Diskkeeper, and PerectDisk 7.0 and I think PerfectDisk 7.0 is by far the best as it rearranges files depending on how much they are used. Your boot files are put in the front of the hard drive and lesser used files are put in front of those while the frequently changed files are put at the end of the drive so they don't fragment other files when they are updated. But if you dont want to pay for PerfectDisk 7.0 then Windows Defrag or the free version of Diskkeeper would do good.