2. Press and hold Home Button ( middle ) + Volume Up + power on button
3. Wait for 5 second until Android System Recovery menu appear
4. There are 4 options
reboot system now
apply update from sdcar
wipe data/factory reset
wipe cache partition
5. Move the options to " Wipe data / factory reset " using volume down ( - ) button and menu button to confirm, because the touchscreen doesn't work in reovery mode
6. After the process done, phone will reboot.
