It is much easier and reliable to use standard Notepad application for configuration files editing.
If something goes wrong and the boot-off script does not work properly, remove the defrag_native entry from the following system registry parameter manually:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\BootExecute
The volume analysis algorithm was generally the same prior to 3.2.0 version of the program. Since the 3.2.0 version UltraDefrag uses the Ultra Fast NTFS Analysis algorithm. It reads MFT directly and analyzes them to retrieve detailed information about all the files contained on the volume. This algorithm is much faster (approximately 25 times faster).
Defragmentation is done in different ways. MyDefrag tries to optimize files placement using original algorithm that is complex enough. On the other hand, UltraDefragmenter was designed to be as fast as possible, therefore it simply tries to move all fragmented files to free space areas. Nothing more. The volume optimization command was added primarily to enlarge the free space area in the terminal part of the volume for future defragmentation success.
The best advantages of UltraDefrag are an ability to defragment system files at boot time and well readable reports. Also UltraDefrag has a handy graphical interface. And is licensed under GPL, and always will be an open source software.
The main disadvantage of both applications (UltraDefrag and MyDefrag) is that they are based on MS defragmenting interface that has very ugly implementation. We cannot change them because it is a part of the filesystem drivers (ntfs.sys, fastfat.sys) that are too complex and not open source to modify or replace them.
The progress bar measures disk space, not the number of files. So when few big files are analysed, the progress bar will increase very fast. Conversely, when a thousands of small files are analysed, progress will be relatively slow.