Did I say the upgrade had been fairly painless? Allow me to revise, in view of a tiny gem called dxwebsetup.exe.
That tasty little morsel was quite familiar to me in the pre-Vista (2010 and earlier) era, as you used it to make sure that all your DirectX stuff was up to date, but was never well publicized, so anyone non-tech savvy with a DX issue would be stumped until they found a guru (ie. me) to fix it for them. It got added to my preliminary support checklist (along with "did you turn the stupid thing off and back on?", etc.).
This DirectX update process was, at the time, done separately from other Windows stuff. When the unified Windows Update along, no more need to bother with that (so it faded into my memory banks, keeping company with other great stuff like dealing with DIP switches, jumpers, and IRQ conficts in a DOS4GW environment).
So, as I was going through the stuff I'd imported from my Win7 install, there were a few games (eg. Spintires) that failed to work due to missing dx9 files. "No problem", thinks I, "it's probably in the redistributable packages that came with the game..." so dig them out, try it, and ... no. Hmmmm.
OK, head online and search for one of the missing files, d3dx9_43.dll. Hey nifty, first result is from M$, entitled "D3DX9_XX.dll is missing. What do I do?". That should do it! It says I have to run dxwebstup.exe, available at a link provided. Click the link, and it takes me to ...
The Win10 main download page, as does
every other link to it. M$ doesn't want you to put nasty old pus-filled DirectX9 files on your beautiful, fast, new, DX12 machine, so
you can't even reach those pages if you're searching on a Win10 machine. FFFFFFFFFFFFFFUUUUUUUUUUUUUUUUUUUUU..............
Fortunately, old drive has a copy (from XP days, by the filedate), so fire it up, it connects, says, "Oh, yeah, there's a bunch of stuff missing", spends eight entire seconds downloading about 60MB of files, "Computer needs to restart to finish updating files", hit "OK", and look at a "Preparing Windows, DON'T TURN OFF YOUR COMPUTER" with a little spinny thing under.
An hour later, still "Preparing Windows, DON'T TURN OFF YOUR COMPUTER" with a little spinny thing under. Oh for fs.
Half hour later (I've given up and am preparing for bed, "razzenfrazzendeal with this crap in the AM"), I hear a beep!! It's rebooting!! :squee:
TL;DR, everything's better and working, everything I've tried runs as well or better than in 7, and computer's about 80% set up the way I want it. And, yes, if I'd just gone and upgraded my Win7 install, instead of futzing around trying to get this dual-boot working, it probably would have much faster and easier. Will I learn from this for the next time? No.