I don't usually think about hard drive defragmentation programs as being exciting, but this one is an exception. JkDefrag itself has a number of features that I have not seen in other free defrag programs, and JkDefrag GUI is a well designed program that makes these accessible and easy to work with. Here's a quick listing of some of these:

- The screensaver option: although JkDefrag does not continuously defragment your hard drive as a process in the background, the screensaver option goes one better in that it kicks the defrag process into action at those idle times when normally your screensaver would run (and will show the visual representation of the defrag process as the screensaver). Extremely cool! This is my favorite feature simply because it provides an automatic install-and-forget solution to hard drive defragmentation. (Note that you can install the screensaver from the 'install' tab in the GUI).
- Space hogging files: JkDefrag will push files certain files behind directories and regular files to make system operations faster. These space hogging files include files that are 50 megs+, most compressed archive filetypes, data in the recycling bin, and a number others (for a list of the default space hogging files go to the JkDefrag site and look for "what are spacehogs"). Note that you can use the GUI to manually add more filetypes (e.g. avi, mpg, etc.) to the list of Space hoggers if you want.
- Portable: a U3-specific version of JkDefrag GUI is available.
- Safe: ok, so this isn't a unique feature but a good one to highlight all the same. JkDefrag uses Microsoft's standard defragmentation API library (which most defrag programs use) and is extremely safe. When interrupted, the defragmentation process will finish the immediate task at hand in the background and shut down