Unless they fixed it in some patch, Nvidia drivers always force 16-235 when using HDMI with common HD resolutions (720p, 1080p). You can change settings in your control panel all you want but it won't make a difference. At least, that's been my experience and that of many others when searching for a solution. The only solution was creating a custom resolution that's outside of the normal HDTV range (like 1920x1079).