With the phone turned OFF

Hold the CENTER of VOLUME button, then press the END/POWER button and release it.
Or
Remove the back cover and the stylus to reveal the RESET button (it’s located at the bottom of the stylus compartment).
Hold the CENTER of VOLUME button, then use the stylus tip to press the RESET button.

Then follow instructions on the display

With the phone turned ON

Tap Start -> Settings -> System -> Clear Storage
Enter “1234” and then tap Yes.

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