JkDefrag GUI: Windows screen saver lets you defragment your hard drive
That's where JkDefrag GUI comes in. As you could probably guess from the "GUI," the program is a graphical user interface for JkDeFrag. The utility makes it easy to customize your defragmentation tasks, with a variety of options.
You can analyze your hard drive usage, defragment, and/or arrange files on the disk. You can schedule regular defragmenting tasks. And our personal favorite trick is that you can set jkDefrag as your screen saver. When your computer's been idle for a few moments the utility will kick in and start optimizing your hard disk. Seeing as most monitors don't really need "saving" these days, it's a pretty good use of your spare CPU cycles.
You can run JkDefrag GUI as a standalone application, or use the options under the installer tab to install the program and screen saver.
[via freeware genius]