To completely reset the system back to factory you generally hold the reset/reload switch for 5 - 10 seconds.
WARNING: Factory default language is German. When you reset back to factory defaults the language of all the prompts will be German. Be sure you know the procedure for setting the language back to English (or your language of choice) before you begin. Resetting scrubs all the data - make sure you have a backup of all your data/database functions before beginning.
This works for the OfficePro, OfficeCom and OfficePoint, so I assume it works for the office one as well.