Are you familiar with the NVIDIA control panel? If not run Minecraft, then quit and right click your desktop and click NVIDIA control panel. Click "Manage 3D settings" on the top left, then choose "Program settings". Click on the "Add" button and add the Java Platform SE Binary. Then use the scroll bar to go down in the list of settings, and find 'CUDA - GPUs' and click on the setting. Choose only the video card you want, and then click 'Apply' in the bottom right. See if that works.