In order to hard reset a Nokia Lumia 925, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Nokia Lumia 925 device will be brought back to the default configuration of a brand new device.
1. Power off the phone.
2. Press'n'hold the Power and Volume down buttons.
3. Let go of them when the device vibrates.
4. Exclamation mark will appear. When it does, press this button sequence: Volume Up > Volume Down > Power button > Volume Down
5. Phone will reset and restart. Voila, done.