Vista Ultimate x64, 8800GT, 180.48 drivers. When I try to change flat panel scaling from "Use my display's built in scaling" to either "Use NVIDIA scaling" or "Use NVIDIA scaling with fixed-aspect ...

Usually single GPU is the safest default. If you want to play with SLI settings for a given game without a profile, create a profile for it and set the SLI mode there. Generally speaking one of the ...