Press Home & Power for 15 seconds
Keep the Power Button and Home Button depressed for 15 seconds until you see the Apple Logo.
If the Apple still does not come up, then connect your iPhone to Wall Charger, let it be attached for 30 minutes. Now press Home & Power for 15 seconds, you should see Apple, do not release keep it depressed, then you will see Connect to iTunes. Now release and Connect to your PC/Mac to restore with iTunes.
If nothing helps go to Cupertino iPhone Repair and call them @ 408-490-1446, see if they might be able to help you. I have used their service in the past.