UltraDefrag is powerful Open Source defragmentation tool for Windows NT. It's engine is very fast, because it is created as kernel-mode driver. They are three interfaces to them: graphical, console and native. First is very useful, because it use cluster map visualization.
Console is good for task scheduler, and native tool - for advanced users and programmers. Design of the UltraDefrag is very ergonomic: no skins, no localization, no animation and so on. It's true small and powerful program! It can be used on Windows 2000, Windows XP, Windows Server 2003 and Windows Vista. NT 4.0 support is currently unavailable.