You have to enter its service mode to do a factory reset. If you wish to get some details; check the site linked here. Viewing it in "
Mosaic" or "
Magazine" will make surf easy Pull up older posts. Surf the site with patience.
http://electronicshelponline.blogspot.com/
Service mode entry, adjust and exit procedure to many popular brand devices are given. Never forget to exit the service mode, after all adjustments have been done.