UltraDefrag 9.0.1 was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The actual developer of the free program is UltraDefrag Development Team.
The program's installer files are generally known as dfrg.exe or ultradefrag.exe etc. We recommend checking the downloaded files with any free antivirus. The most popular versions among UltraDefrag users are 9.0, 7.1 and 7.0. UltraDefrag lies within System Utilities, more precisely HDD Management.
From the developer:
UltraDefrag is a disk defragmenter for Windows, which supports defragmentation of locked system files by running during the boot process. It is easy to use without any complicated scripting or a huge load of configuration settings. You can filter the files processed by size, number of fragments, file name and path. You can terminate the process early by specifying an execution time limit.
You may want to check out more software, such as ConCat, Disk Space Inspector or PassMark Fragger, which might be related to UltraDefrag.