Question NVIDIA driver installation issue ?

Hello.
I understand that I have to ask this question in Legacy section, but it is very quiet there and question is general.

Since I am on old Windows 8.1 (don't suggest upgrading/updating), I cannot install latest drivers.
The last driver from NVIDIA (version 475) installs on my PC, but then Windows does not see it and is using crappy Intel driver. However, I was able to roll back to version 436. WIndows actually did that automatically during a slow agonizing reboot, but WIndows installed only the driver, not the whole package.

Everything is working when Windows boots up, but I am trying to fix booting into Windows and prefer to clean install drivers as much as possible, plus I think I need to install the full driver package, not just the driver.

What will happened if I take exactly the same driver as the one currently installed by Windows and attempt to do a clean install, will it simply delete the existing one and install the same one, but in a controlled environment, or will it refuse since drivers are the same, or will it create more mess?

Thanks.
 
GTX 970, 4790K, Asus Maximus Hero VII.

I have very slow boot, about 5 min. Selective start up with just a few drivers to load. My previous GPU crashed and died. Also, I have this slow boot up issue for a while, I think GPU was dying for a while, PC was crushing few times a month with screen going black....
So I decided to start straighten things up from GPU drivers.