Did you tried to put the iPhone in recovery and/or DFU mode? Follow this guide (from the net): Step 1: Launch iTunes. Step 2: Plug your iPhone in your computer via the USB cable. Step 3: Turn off your phone. Step 4: Hold the Power and Home button together for exactly 10 seconds. Step 5: After 10 seconds, release the Power button and keep holding the home button until iTunes tells you it has detected your iPhone.