Search unique files is very useful for those who perform clean installs of various types of software.
Load a directory, choose the criteria for how you want to search for unique files, and select "Unique Files" from the "Scan for..." button or from the "Control"menu.
Once you have the list of the unique files you can use the "Mark/select Options" window to search inside the list of found files.
One possible use is:
If you install a new System with the clean install option, and you want to move old extensions, Control Panels, Preferences... etc. to the new folders.
Load both folders and scan for "Unique Files", when the list of found items appears choose "Mark..." item from the "Control" menu and choose the location you want to mark, and successively move to, to the location you want the marked items.