While i don`t know the driver version you`re using for your GTX 460 . If you`re using any beta version then install an older version of the WHQL drivers from Nvidia 296.10 or previous but no earlier than 275.33 . Also there should be an option to clean install the video drivers from the options menu . Additionally if you don`t use 3D then do not install the 3D drivers . Are you overclocking your card ? You can make an exception in your antivirus for Witcher 2 just in case real time scanning is affecting the game .