How To Hard Reset Nokia Lumia 920

You have nokia lumia 920 and want to format/Hard reset your phone then you follow these instuctions
*** You save all contacts in PC or in other nokia mobile
** Check other impotent files in phone memory and todo list
* Now you Switch off your mobile

see also-How to Hard Reset Or Format Samsung Galaxy Ace S5830
* Now press and hold Volume down and power on/off button until phone vibrate ( in WP 8)
* Your phone vibrate 3 times and start
In window phone 7
* you press and hold Volume down and camera and power buttons until phone vibrate.