My notes, things I have learned, and documentation I have created.

Select Start/Accessories/Clear Storage
Enter 1234
Select Yes

OR

Turn the phone off
Press and hold the dashes to the left and right of the red and green phone buttons.
Press and hold the power button for a couple seconds while holding the buttons above.
Release the keys.
You will be prompted you to clear storage.

Source: http://www.good.com/faq/17957.html