Try these fixes if, for example, your phone freezes or does not switch on, if an app crashes, if you have sound problems, or if the screen is blank:
1. Restart your phone.
This does not reset your Microsoft Account (Windows Live) ID or remove any personal data.
- Switch your phone on, if possible, and disconnect the charger.
- Press and hold the Power and Volume down keys simultaneously until the phone vibrates. Release and the phone will restart.
2. Reset your phone.
Warning: This erases all personal content on your phone and restores the factory settings.
- Make sure the charger is disconnected, and switch the phone off.
- Press and hold the volume down and camera keys.
- Press and hold the power key.
- When the phone vibrates, release the power key, but continue holding the volume down and camera keys, until the phone reboots.