Format/hard-reset refreshes the phone to original settings, wiping any user data from phone-memory. There are four possible ways to format Nokia smartphones – via phone’s settings menu, by reset codes, by specific key-combos and by flashing. Here we will discuss the first and the third one.
Here is the method to format/hard-reset the Nokia Windows Phone devices (Lumia 800, 610 and 710) by using physical (hardware) keys –
Switch Off the phone completely (Go to step 2 below if it is already switched off)
PRESS and HOLD following three phone buttons, SIMULTANEOUSLY
VOLUME DOWN + POWER + CAMERA
Keep pressing all the three keys (described above) until phone vibrates, now release the POWER