What does the Nvidia driver service actually do anyway? I used to disable it and never had any problems. I think starting with the 260 or 280 series drivers the Nvidia control panel no longer works with the service disable, so now I put it in manual mode. It stays off and starts automatically when you run the control panel, and I still don't have any problems in games with it not running. I rarely go into the Nvidia control panel, and if I do I stop the service when I'm done. Any custom settings for a game still get applied with the service stopped.