"iPAQ 3100, 3600, 3700 - Remove any expansion packs. Slide open the battery door on the lower left and slide the little switch to the right. Wait 30 seconds and slide it to the left again and plug the iPAQ in.
iPAQ 2200, 3800, 3900, 5100, 5400, 5500 - Turn the device on and remove any expansion packs and/or memory cards. Press and hold down the outermost right and left buttons and then press and hold in the soft reset button with the stylus. Wait until the screen fades completely out and wait 30 seconds. Now, plug the device in and press the soft reset button. Note that this will not clear the iPAQ File store. You will need to launch File Explorer and manually delete all data in there. Some report that you don't need to apply power, simply do a soft reset. I know you need to on a 3900, but later devices like the 5500 and 2200 may have removed that step. Applying power won't hurt, but if it doesn't work on the battery, plug it in then soft reset"
