No no no, you gotta upgrade to 10 first, then make a bootable ISO if you're into the clean install thing. 7/8/8.1 keys won't work when you're installing a fresh copy of 10, so don't jump straight to a fresh install.
What's happening is when you upgrade, your old key is "converted" to a 10 key and it stays recognized on that machine, even after you decide to format and slap a fresh copy of 10 on it.
Check your drivers one last time, Bob, look up your model under the manufacturer's support page, and check you're running all the latest stuff. With display drivers, go to Intel/NVIDIA/AMD and check against their sites. And then try one more time.
Last resort would be, as Charlie points out, slap a fresh copy of 7 on your drive and upgrade from there.