My HP G72-227 started flickering and going black. Then it stayed black. Power goes to the optical drive but the USB slots don't work. Fans come on. I have tried doing the battery out, disconnect anything hooked up, press power button down for 30-60 secs then plug in adapter Still nothing. I have tried doing it at different lid angles- still no screen. Hooking up an external monitor won't work, because the ports don't work. Help!!