I upgraded to win10 months ago and it was working. Occasionally I would get a totally black screen, but using the win, ctrl, shift b combination I could get enough control to reboot and that generally fixed the problem. However today when I use the combination the screen displays for just a few seconds and then goes blank again. Multiple (painful) reboots and the problem is still manifest. I've tried safe boots and a number of other attempts but I'm unable to get my system usable. I have an hp pavilion desktop using the video from the motherboard. Any suggestions?