Nokia Lumia 900 hard reset
First try this to soft reset your Nokia 900 Lumia. Press and hold the Volume down and Power buttons until it vibrates, after that you have to release all the keys then phone will vibrate 3 times.
To hard reset your Nokia Lumia 900 using key combination
Turn off your Nokia Lumia 900. Press and hold the following buttons Camera + Volume down + Power until your phone vibrates, then release only the Power key and keep pressing the Camera + Volume down for a couple of seconds 4-5s.
- On the Start screen, tap .
- Tap Settings > about phone.
- Tap reset your phone, and then tap yes.