How to manually switch between Two Different NVidia GPU Cards - Windows 7

There's not much else that you can do besides what you've done already. Under windows, GeForce GPUs (all of them) are governed by the WDDM environment. The biggest single imposition of this is the Windows TDR mechanism (which can be modified, albeit with registry hacking and perhaps trial and error). Other than that, simply avoid having a desktop built on the GPU you want to reserve for CUDA, and then doing appropriate detection and cudaSetDevice() is sufficient.

To answer your question directly, given that WDDM cannot be shut off, and it has at least some side effects (TDR is one of them) no there is no way to completely disable OS interaction with a GeForce GPU under windows, such that the only time the card experiences any OS interaction is when a CUDA context is created on it.

And yes, this is off topic for stack overflow, which is why the close votes are there.

Yes. Very simple. USE THE HARDWARE configuration.

They hid it in Windows 7: Its now in Power Configuration. http://windows.microsoft.com/en-us/windows7/change-create-or-delete-a-power-plan-scheme

Have one power scheme with one video card, and the other hardware configuration with the other, and get a cheap V switch.

http://www.avsforum.com/t/1395418/cheap-dvi-kvm-switcher