I have a GeForce GTX 570 GPU installed in my machine. I installed the CUDA Toolkit and SDK (version 3.2), and everything worked fine. I ran a number of the examples (including building them) and they also worked fine.
In order to use Parallel Nsight, I installed a second GPU (an old Geforce 2) in a PCI slot to handle the display while the GTX 570 handles all of the GPU computing. In the BIOS, I set PCI to primary display, as I want the GeForce 2 to handle display. Now I cannot run any of the CUDA examples, and any calls to cudaGetDeviceCount return 0.
Both cards still show up in Device Manager, and are reported as working correctly. I performed a clean install of the latest drivers for the GTX 570 (266.58) and this did not correct the problem. Additionally, I cannot open the NVIDIA control panel. Clicking on it, either from the Windows control panel or the file location, does nothing.
Does anyone have any idea what might be happening here?