I believe the Windows defrag utility in XP was indeed based on a watered-down version of Diskeeper (of around 2001), but the Vista and Win7 versions are not related to Diskeeper AFAIK. From what I read, the code was written from ground up by MS, and they also removed several features like the drive map and detailed analysis from the GUI, which were present in the XP version. The newer versions of Diskeeper automatically defrag in real-time using idle system resources, while the windows defragger starts on a predetermined Task Schedule. The former also has many more useful features..it's faster
