UltraDefrag is powerful Open Source defragmentation tool for Windows. It is very fast, because the defragmenting is done by kernel-mode driver.
They are three interfaces to them: graphical, console and native. The GUI is very useful, because it represents your filesystem visually as a color coded cluster map. The console is another option for those that prefer the command line. It is also allows you to run UltraDefrag from the task scheduler and scripts. Finally, the native executable will run at boot time in a manner similar to chkdsk.
The design of UltraDefrag is very simple. There are no skins, localization, or animations. It is a small and powerful program!

Features of UltraDefrag 1.4.0 :
· Very fast defragmentation, the work is done via a kernel mode driver which has an optimal defraging algorithm.
· Very small engine written in pure C.
· Nice graphical interface - compact and functional.
· Safety, because the file moving is accomplished with Microsoft's own Defrag API.
· Simple to use.
· Ability to generate html reports of fragmentation status.
· Ability to include/exclude files based on simple filters.
· Native x64 support.
· Free: Distributed with full source code under the GNU General Public License.

What's New in UltraDefrag 1.4.0 :
· i18n support was added
· gui program was translated into Hungarian and Russian languages
· documentation was improved
· program settings were moved to one file
· gui design was improved and simplified
· console program's option -l was added
· many significant bugs were fixed (possible buffer overflows)