Do Not Attempt this unless you absolutely have to!
Go to Start, Accessories, Clear Storage, type in 1234, and press yes.
With the device off, hold down the right and left soft keys and then press and hold the power button. Once a black screen shows asking you a question, release the power button and then the soft keys. This is your last chance, if you want to reset the device COMPLETELY press the Send key. Otherwise press the End key.