On Your Computer, in iTunes you will see:
"There is a problem with the iPhone/iPad/iPod that requires it to be updated or restored." Click "Restore" Click "Restore and Update" Click "Next" Click "Agree"
You'll see "Extracting Software" and "Waiting for iPhone" at the top of iTunes.
Depending on the speed of your Internet connection your device can be erased in 15-20 minutes or it can take over an hour.
- iPhone/iPad/iPod Recovery Mode
- iTunes is restoring the software on this iPhone/iPad/iPod Touch.
If you feel you had software or compatibility issues with your device, it's best to set it up as a new device rather than restore from a backup.