Hi Whoosh7,
As I've discovered, through exhaustive testing, you appear to have been correct... It may even have been reading your earlier post that set me off on that very long and excruciatingly painful tack..... thank you very much!! :) :) :). Anyway, if anyone made you feel that you'd been shot down in flames they weren't worth listening to - even if they are technically more knowledgeable than you (and me)!
I'm as certain as I can be regarding the missing or corrupt nForce 750i drivers required by my motherboard - short of any confirmation from Microsoft..... and I don't see any signs of that happening any time soon. I'm just waiting for the Fall update to see if the problem gets fixed or history refers to it as the Fail update.
You don't say whether you're running 32bit or 64 bit Windows 10 but assuming the latter....
I took a quick look at the specs of your Asrock g31m-gs motherboard and, as the chipset is from Intel, I'm doubtful that you will experience the same issues as I'm having with my Asus P5N32-E SLI Plus. If you read back up here, a similar Asus motherboard... but with and Intel chipset... seemed to be working fine. That said, the last driver update for your motherboard was back in 2009 so it may well be on the list for EoL in the future. However, the drivers were updated to support Windows 7 64bit but a later generation generation of Windows 8 64bit drivers failed on my motherboard when I tried to force feed them during an install.... the 322nd if I recall correctly. :)
As for the your graphics, it's possible that the on-board NVidia may suffer the same fate as the aging Intel chipset but the drivers for your GTS 250 were updated to support 64bit Windows 7 in 2016 so they will probably remain supported for a while yet....
Of course, at some point in the future, you may well end up with a graphics card that remains supported by Windows 10 64bit in one hand, staring at a motherboard that previously worked perfectly well with Windows 10 64bit in the other but is no longer supported
- if it's any comfort, you'll not be alone!
Best of luck.
Cheers
p.s. your final comment regarding using a USB to install got me thinking.... again.... which build was it that succeeded? Also had you previously tried and failed with the same build using a DVD ISO?