First method:
- First of all, switch off the mobile phone by holding the Power key for a few seconds.
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- Then press and hold together Volume Down and Power button.
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- When you feel the vibration, immediately release the Power key and keep holding the Volume Down button.
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- You can release this button when you see a large exclamation mark.
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- In this step press the following sequence of buttons: Volume Up - > Volume Down - > Power - > Volume Down.
- Good job! Tha hard reset has just been performed.
Second method:
- If the display is off, press the Power to turn it back on.
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- Go to Windows Phone Settings.
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- Afterwards select About.
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- To confirm the whole operation tap Reset your phone.
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- Well done! It may take a while to finish the hard reset.