Black Screen. Driver off.

I have a Dell XPS 9550-100 laptop, running windows 10.  It has both Intel 530 and an Nvidia graphics driver.  When I turned on the computer today, it displayed only a black screen.  I was able to get into the computer by attaching an external monitor and logging on, and found that it was calling the external monitor display #2, and both that and the laptop screen (black) were being driven by the intel 530 driver.  I updated the driver, but that didn't help.  I then tried disabling the Nvidia driver, but that didn't seem to change anything.  So I turned that back on and disabled the intel driver, hoping maybe the Nvidia one would work properly.  Now I have a black screen on the laptop and a "no signal" indicator on the external monitor.  Halp!

(cross posted at https://forums.intel.com/s/question/0D50P00004EWzgnSAD/is-there-a-way-to-enable-the-intel-530-driver-without-seeing-the-screen)