Windows 8.1 64-bit driver for Coprocessor on Mid 2009 Macbook Pro 5,4

I have successfully installed Windows 8.1 Pro 64-bit onto my Mid 2009 Macbook Pro 5,4. The installer from BootCamp 5.0.533.5033 would not run, but I installed one-by-one the files under Apple and then ran the 64-bit nVidia installlers. I have everything present and accounted for except for the 'Coprocessor.'

I have looked through the forums and everything seems to indicated that if you install the nVidia drivers it will install the driver for this but it doesn't. Any thoughts/suggestions/solutions?