In order to hard reset a Nokia Lumia 525, 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 525 device will be brought back to the default configuration of a brand new device.
1. Turn off the phone.
2. Press-hold the Power & Volume down buttons. Release them when the phone vibrates.
3. When exclamation mark appears on-screen, press these buttons: Volume Up > Volume Down > Power button > Volume Down
4. Well done, the phone should now reset'n'restart.