The device doesn't exactly work like a computer... It needs battery power to "remember" what the user does. When you remove the battery, you let it forget everything. It's like how your car stereo loses it's memory channels whenever they do battery related work. What I would HIGHLY suggest, is set Activesync to do a full backup EACH TIME the device connects (it's in Tools, Backup). THEN, when he loses the information, you do a full restore. That being said -- to do a "reboot" just push the reset button (small hole on bottom left side grip) with the stylus. If you want a more thorough reboot, it's safe to just take the battery out for a few seconds. I do this about once a day.
Usually answered in minutes!