Turn your device off.Remove SIM card and MMC card (actually, you do not need to remove these, but after format remember to format memory card and reboot phone). Press and hold 3 keys; Green dial key, * Star key, no. 3 key on keypad Together. Turn your device on while you are pressing the three buttons. You should now see "Formatting .." on the Screen! Leave the buttons now. all thedata on the phone will be deleted.