Brightness controls not working on a Sony Vaio VPCY2

1) Open a terminal

2) type this: gksudo gedit /etc/X11/xorg.conf

3) Enter your password; a text editor will appear, find the following lines:

Section "Screen"
       Identifier     "Screen0"
       Device         "Device0"
       Monitor        "Monitor0"
       DefaultDepth    24
       Option         "RegistryDwords" "EnableBrightnessControl=1"
   SubSection     "Display"
       Depth       24
   EndSubSection
EndSection

4) make this line look like this or add it if it dosen't exist:
Option "RegistryDwords" "EnableBrightnessControl=1"

5) close & save changes (Be careful before saving you can take down your system, if you're not sure that you didn't do anything wrong choose "don't save"!!

6) Restart computer.