I'm certain that what I am about to tell you will work.
Okay, start off by connecting the iDevice into the computer that will be doing the resetting process and make sure that the latest iTunes is downloaded and opened on that computer (does not matter if it's mac or pc). Once that is done, begin holding the home + power buttons for exactly 10 seconds (the power/sleep button is the top button and the home button is the square at the bottom of the phone) then release the power button, but continue holding the home button until you get a message on the computer that says "iTunes has detected an iPod/iPhone in recovery mode. You must restore this iPod/iPhone before it can be used with iTunes." That is when you hit the OK button and just follow the on-screen instructions iTunes provides. After you get that message it's a breeze.
If you fail to get the device into DFU mode, try again. It will give you that message in iTunes.
That should do a full restore.
Good luck mate,
Kunducted