My MacBook powers on, and I can hear that it is running, but the screen is completely black with no video.

1.     connect power to laptop

2.     connect external monitor, mouse, and keyboard to laptop

3.     turn monitor on

4.     press power button on laptop and close lid as quickly as possible

5.     you will get video on the external monitor

6.     allow boot process to complete, then open laptop screen

7.     screen will flicker momentarily, then video will appear on laptop

8.     restart laptop, once it comes back up and video is working, unplug external devices and laptop is ready for use at this point.