Default [Q] Username under Windows Mobile 6

I am using Trimble Nomad devices running window mobile 6. I want to assign user names associated with a password, just like on Windows 7. I am using a GIS software called ArcPad, and want to fill some field in data collection form with the pre assigned username. I wan also limit some usernamer to different role( user and administration) so that they could not change some settings like time, owner etc. Any Idea to do so ?