Perform a soft, factory, and alternate master reset of the device.
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INSTRUCTIONS & INFO
A master reset reverts the device back to factory settings. It will permanently erase all personal data, preferences, settings and content such as pictures, ringtones and apps that are saved to the device. Data stored to an SD card will not be erased unless otherwise selected. It is recommended that you save (backup) important data before proceeding.
From the Start screen, swipe in from the right edge of the screen to reveal the Charm bar.
Tap Change PC settings.
From the "PC settings" screen, tap Update and recovery.
Under 'Remove everything and reinstall,' tap Get started.
Select Desired reset. Note: You must have the device plugged into a power source as this process can take up to a few hours.