UltraDefrag is powerful Open Source defragmentation tool for Windows NT. 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.