Can't control backlight of display

Hello! Installed Windows 7 (64-bit) as an additional operating system using BootCamp drivers. Everything works. But, if I update the videocard driver, it becomes impossible to control backlight of display. Drivers official, from nvidia site. Backlight level at maximum always. Eyes get tired, too bright. Has anyone encountered similar? Know how to solve? May have some ideas? With old videodriver I can't work, becouse it's too old. New bootcamp don't support my computer.

Sorry for my english, I don't know it well.