From Retro Arcade Guides

NARS (NARS Advanced ROM Sorting, a recursive acronym), is a set of Python scripts that allows you to filter your ROM collections to remove unwanted ROMs from XBMC's launcher plugins like Advanced Launcher, ROM Collection Browser, or any other front-end. If the ROM collections are updated or a new version of the emulators installed (which may require some new ROMs to be updated) NARS is able to synchronize the ROM directories of your HTPC quickly and effectively.

If you use Linux or Mac then you will have Python already there, open a terminal and you are done. If you have Windows then you will need Python: I recommend you to install Cygwin.

NARS was previously named XRU (XBMC ROM Utilities). The name was changed due to XBMC/Kodi copyright issues.

This utility was created by Wintermute0110.