We are using a nVidia GeForce GTX 260 graphics card and attempting to adjust the gamma settings. We want to adjust gamma using the video and tv settings, but they are locked/grayed out. The only gamma setting we are allowed to adjust have a restricted range with a high end around 1.5. We need to go up to ~3, which the video and tv gamma setting option would allow us to do, but, again, we can't change this option. Does anyone know how to unlock the video and tv gamma adjustment for this graphics card?