Sometimes your iPad will not be recognized by iTunes for a restore, or boots to a blank screen. DFU mode might be necessary to reinstall the iPad firmware. To enter DFU mode:
1. First run iTunes on your computer.
2. Now plug the iPad into your computer with the USB cable.
3. Press and hold down the sleep/wake (power) button and the home button at the same time.
4. Hold them down for 10 seconds.
5. Release the sleep/wake button but continue to hold down the home button for 5 more seconds.
6. The iPad screen will stay black, and iTunes will prompt that it has detected an iPad in recovery mode.