Switch off, Pull battery.
Insert battery and Press Power Button
Hold Volume up+Volume down together
you can see 2 option
RECOVERY MODE
FACTORY MODE
You will then boot into recovery mode , use volume keys to navigate up and down and power key to choose.
Choose Wipe DATA
Choose wipe cache.
Reboot device.
[ame=http://youtu.be/7QNvDFGv_ME]VID 20140928 130037 - YouTube[/ame]
