UltraDefrag is an open source disk defragmenter for Windows NT 4.0 and later operating systems. It makes use of the same defragmenting API used by many other windows defrag utilities, both open and closed source. However, UltraDefrag has many features that makes it unique. Firstly it has a kernel mode driver that does most of the work, secondly is the ability to run the application at boot up time in a manner similar to chkdsk. This allows for faster defragmentation time and the ability to defragment all files including system files. It can also defrag single file or multiple directory and can generate a list of all fragmented files. The program is available for both 32bit and 64bit version of Windows running on both AMD and Intel based processor.