Pardon my verbosity, but I want to make sure myself clear.
My computer is your basic homebrew office desktop: Asus H87-M-E MB with Intel Core i5-4430 CPU @ 3.00GHz, 8 GB RAM in a Cooler Master Case the size of a doghouse. No neon or gaming stuff, but it worked perfectly. Then Windows 10 suddenly refused to boot, stopping at a black screen. My Windows 10 repair DVD, which always worked perfectly, couldn't boot the machine. Just a black screen. Neither could the installation disk; it gave me a picture of a window, some energetically swirling dots and then a black screen. Meanwhile, since the system was dual-boot with Linux Mint, I could get online that way to look for help. (As much as I hate Linux, I have to admit it worked perfectly through the whole mess.)
Finally I reinstalled Windows 7, which booted from its install disk just fine. To avoid losing the 20-odd years worth of music, programs, videos and documents I've accumulated, I installed the Windows 7 in a different directory than my old Windows 10. After it was working, I found that my old boot disk wasn't showing in File Manager. I had to find it in Disk Management, assign it a drive letter and tell File Manager to show empty disks just to see that it was now totally, completely empty. Various disk tools found no errors on it, Disk Management proclaimed it 'healthy' but it's empty!
Now what I am trying to figure out is whether or not I can blame Windows 10 for my problems. I liked it fine, when it worked. Is it Windows 10's fault my old C: drive is blank? Can I safely upgrade to Windows 10 now, and start all over again. I don't want to miss the window for the free upgrade.
Why didn't Windows 10 install when everything else could? Is my blank boot disk related to my black screen?