A factory reset will restore your phone to its out-of-the-box settings.
Note: A factory reset will delete your personal data and settings — including contacts and photos. To prevent data loss, make a back up of your device before you do a factory reset.
Note: If you want to preserve the data stored on your SD card, remove the SD card from your phone.
Go to the Start screen.
Tap the menu symbol.
Tap Settings.
Tap Backup & reset.
Tap Factory data reset.
Tap RESET PHONE.
Tap ERASE EVERYTHING.
All data and settings saved on your phone will be deleted.