The 177.x driver branch has very poor performance (this is valid on windows aswell). Grab the 180.22 from http://www.nvidia.com/Download/Find.aspx?lang=en-us and disable Xinerama. Figuring out what the original problem is (what made you revert to 177) would be a good start. As for the registry keys, if they are missing in your registry, their default value is used.
