FACTORY DATA RESET IN ANDROID

Hard reset can be done in 3 ways:

1. Go to Settings –> Privacy –> Factory data reset. This method is valid for all the mobile phones. However, many users have experienced problems in resetting the phone using this method. Also, please note that this method only does a factory reset.
2. Hard reset using a hack code: *2767*3855# — Dial this code on your phone. Please note: DO NOT TRY THIS for testing purpose unless you are sure what you want to do. This code does not ask for a confirmation.
3. Factory reset using: *#*#7780#*#* — Dial this code on your phone. This will ask you for a confirmation before resetting.

It is highly recommended that you take a backup of your data if you are not sure ! You should remove the SD card before you reset your phone so that the data on the SD card is not lost !


Source : http://varunverma.org/tech/android/hard-reset-your-samsung-galaxy-5/#more-386