Black screen on Windows 10

I have a computer with Wndows 10 upgrade from Windows 7 installed.  
Ever since the upgrade, we've had trouble with the graphics.
Now on the 4th graphics card which is an ASUS Nvidia GT-710-SL and supposedly well qualified to work with Windows 10.
The computer is an ASUS P5N-d with 8GB RAM, Intel Core 2 E6700 2.66GHz CPU, Phonix BIOS Rev 1401 6/21/2010.

The RAM tests good.
The HD tests good.
The computer boots normally but for the last few days has been "black screening" with no reponse.
I can PING it but not much else.
I have run Knoppix on it and didn't get any black screens - so I really dont' suspect hardware.

Windows restore points won't restore - with complaints about "maybe an AV program running" - which I have disable during those events.
No parasites are evident.
My next step will be to reinstall the OS from within Windows, keeping the files, etc.  and hope for the best.
I have no idea what keeps running and what is failing when this black screen happens.
CTRL-ALT-DEL does nothing.

Telnet doesn't respond and I *think* it's enabled.

Any command-line things I might try?

I can always reboot and run for a while that way but it's short-lived: maybe hours, maybe not.