Black screen with cursor after upgrade from 7 ultimate to 10

I upgraded from windows 7 ultimate to windows 10. It seemed to install okay and asked me to log on and select setup preferences, which I did. I left it alone to finish setup and it went to sleep. Now I only get a black screen with an active cursor. I've tried multiple hard restarts, entering logon blindly as suggested in other posts and using windows key-p to switch monitors all to no affect. Ctrl-alt-del has no effect. I cannot bring up any screen and so cannot start in safe mode or download video card drivers. I do not have Windows 10 on media. Any ideas?

Oddly enough this got fixed, but I don't really know how. Microsoft was no help. Told me to reinstall W7 and update drivers for video card. Ugh. I didn't have the W7 disk so I called Dell, the OEM. Dell had me do a system hardware scan. Fat chance I thought as multiple attempts at hard reboot while pressing multiple function keys and holding other keys down had no affect. But, they had me hold the power button down for 90 seconds, then restart while pressing F12 as many times as I could. I got a test screen and was able to run the hardware scan. No problems were found and none were fixed, but after that the computer started booting up in W10. I was able to get a desk top. It required a couple of long boots and a couple of restarts (automatic), but it is now up and running. The only thing I can guess at is the scan must have interrupted a loop the the computer couldn't get out of.