I am seeing the same black screen after the last windows 10 update. It has something to do with the screen drivers I believe. I had an extra Quadro 500M card laying around and when I popped that in it works at the low resolution you get without a driver. Once I loaded the driver and rebooted it geos black as soon as the login wallpaper is loaded. For some reason it will not work using the normal screen resolution.
I am still getting the same situation every time there is an update. The fix is the same for me. When the computer hangs on a black screen with the activity circle, I wait until there is no hard drive activity and then I turn off the computer with the power button. I wait a few seconds and then power the computer back up while tapping the F7 key (I indicated the F4 key in my last post and I'm not sure it makes a difference). I do this for a long time until it either comes up or the hard drive has again gone inactive. If the drive is inactive I shut down the computer again and then power it up while again tapping the F7 key. So far, it has always come up normal with no more than 2 attempts. Its an inconvenience, but I haven't seen anything else that works better