Tip: How to Clear Everything From Your Windows Mobile
From the Start Menu, choose system tools (or Settings, then the system tab). Click on Clear Storage and you should get an explanation of what you're about to do: namely, blast everything off your device and revert to the factory default.
To ensure it's what you really, truly want to do, the system requires you to type in specific characters before clicking "yes." Tap them in, click the yes button and watch as your device resets.
You'll be prompted to approve a restart and when Windows Mobile comes back up it'll look just the way it did the day you took your device out of the box. Scratches, dings and other physical wear are not nearly as easy to clear.