UltraDefrag is an open source disk defragmenter for Windows operating systems. It makes use of the same defragmenting API used by many other windows defrag utilities, both open and closed source.
UltraDefrag 14 features highly improved disk processing performance, new defragmentation and optimization depth settings, process priority control and a bunch of other settings and improvements.
UltraDefrag Portable is a powerful Open Source Defragmentation tool for the Windows Platform. It can defragment any system files including registry hives and paging file.