Windows contains a good disk defragmentation utility, called Windows Disk Defragmenter. The GUI version (with graphical interface) of the tool, which can be started typing "dfrg.msc" without quotes in Start - Run, is very handy and user friendly, but not perfect:· XP: doesnt allow the defragmentation of multiple units, neither simultaneously nor consecutively.· Vista: files bigger than 64 mB wont be defragmented because their impact on system performance is less relevant than smaller files.If you need to defragment multiple hard drives or partitions (maybe doing something else in the meanwhile) or you want to have a well defragmented hard drive, you can try DefragDrives, an alternative to the standard Windows interface. Also, this application make use of the standard Windows defragmentation engine, therefore there are no doubt regarding its high performance.Utility capable of defragmenting multiple drives using Windows' defrag tool.