When you need to do a hard reset? You can apply this operation in many cases, We will mention some of them here: - After installing bad or unsupported application into your Samsung mobile phone which causes your phone to be frozen. - Your Samsung mobile phone doesn't respond to any order after booting because of some software errors. - Forgotten pattern lock in Samsung Android mobile phones. - Forgotten user code. - Forgotten phone code. - Before or after installing new firmware updates into your device. What to do before performing the hard reset? - In case your Samsung mobile phone can connect to a computer then it is better to make a backup of your saved data using Samsung kies software. - But in case that is not possible then you can check that your phone's battery has enough charging, Otherwise you should charge it. Samsung I9300 Galaxy S3 Hard Reset Steps: - Take out your phone's battery, SIM-card and memory card too. - After 10 seconds put the battery back into your phone. - Press and hold Volume Up key + Home key then press Power key. - Keep pressing the above keys until Samsung logo appears,Then when you see the Green Android Man release all keys. - You will be into Factory reset menu. - Use Volume Down key to select Wipe Data / Factory Reset option. - Use Power key to confirm the operation. - You need to use the Volume Down key again to select "Yes delete all user data" - Use Power key to confirm. - After performing the hard reset, Select Reboot System Now option, And confirm it using Power key. - Now the phone will reboots, Wait for it to be fully on and then you can start using it. Notice: The hard reset operation will delete anything that are saved in your phone's internal memory, So make a backup of your data in case you can access them.