On the bottom left of your iPaq (the bottom being the part you put into the docking cradle) is a little sliding door. Use the tip of your stylus to slide it open. Inside is a small, dainty switch. carefully flip that switch to the other position(towards the middle of the device on my iPaq). Then press and hold the reset button (the little hole on the bottom right of your iPaq) with the tip of your stylus for several seconds. Then flip the switch back to its original position and close the little door.
That switch has been known to break easily. Be very gentle when sliding it from one position to another. It only moves 1-2mm.
The device will revert back to state as produced by the factory. Any other information on the device will of course be lost.
Dan East