First you have to move the ARES_Commander package under the Applications folder to the trash.
To reset the previous state before the ARES Commander installation, you have to delete the folder
/Users/Current Username/Library/Preferences/ARES Commander Edition
with the user specific settings.
The "ARES Commander Edition"-folder contains in the sub-folder(s) with the version number (x.x.xxx) the customization of the pull-down menus, toolbars, workspace etc.. If you delete this folder, the default user settings will be created again at the next start of ARES Commander. It can also contain multiple sub-folders with version numbers of different installations. You can find out the version number of the user specific folder via the OPTIONS dialog and the tab "File Locations".
Further you should also delete the com.graebert*.plist-files with the registry information about ARES Commander. They are located in the folder:
com.graebert.www.ARES Commander Edition.plist
A reset command does not exist. We plan to add the functionality to synchronize the user folder after an update.