To Factory Reset Nokia Lumia 520 for any reason, follow these simple steps. At the end of the steps, i have included a link to download manual for Nokia Lumia 520
– Ensure that your phone is charged, if not then connect it to the charger and let it stay on charge for at least 30 minutes.
– Power off your phone, and disconnect the charger. To power it off, press and hold the power button for 15 seconds.
– Once it is powered off, press and hold the volume down key on the phone, and while still holding it, connect the phone to the charger again. This will result in an exclamation mark (!) on the phone, once this is displayed, release the volume down key.
– Next, press the keys on the follow in the following sequence:
a) Press Volume up (see image above, 1 indicates volume up)
b) Then, Volume down (2 indicates volume down)
c) Then Power, and then Volume Down. (3 indicates power)
Wait for the phone to initialize and load the setup files, this usually takes 5 to 7 minutes. DO NOT PRESS ANYTHING while it is loading, once it has finished loading, the screen will go blank for about 30 seconds. Once it powers back on, go through the setup process.
The factory restore setup is complete.