If you try either option, be sure to come back and let us know if you get a fix for it.
I just don't understand what's going on, like you. Even if you don't install the NVIDIA software, Windows should detect your card and provide a driver for it, albeit a generic one.
If you can boot with your old card, you could try a hot install of the new one after Windows is loaded. If that worked, the only problem I see is that, when you remove the old one, the new one has to be inserted into the same slot as the old one.