With the phone turned off, press VOLUME DOWN + CAMERA key + MENU + POWER key. for 1 minute (Maybe not working!!! Pls confirm...)
Main Menu>Settings>Phone>Phone mgmt.>Factory Settings>Delete Data and Restore.
Type *#7370# then select YES. Default phone lock code 12345
Note: First charge your battery, backup your important data if possible and in most cases take out SIM and SD card. It is impossible to recover your data after doing a hard reset, so online backup is always important. You can also backup your data on your hard drive or a raid system.