Screen brightness not working

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http://askubuntu.com – I use Ubuntu 12.04 on my Sony Vaio(VPCCW2HGX). At the first times, brightness control works well, but after the activating additional drivers(nvidia accelerated graphics driver) brightness control doesn't work. I searched this issue on so many Ubuntu and Linux forums, but solutions doesn't work. I tried these ways: Installing xbacklight, Adding Option "RegistryDwords" "EnableBrightnessControl=1" to /etc/X11/xorg.conf Updating Nvidia drivers To try to change brightness by typing "sudo setpci -s 00:02.0 F4.B=xx" All of these ways doesn't work. I still can't set screen brightness. Is there an (HowTos)