Code:
Section "InputDevice"
# Identifier and driver
Identifier "USB Mouse"
Driver "mouse"
Option "CorePointer"
Option "Device" "/dev/input/mice"
Option "Protocol" "ImPS/2"
Option "Emulate3Buttons" "true"
Option "ZAxisMapping" "4 5"
EndSection
This is the same section from my xorg.conf. As far as I recall, using "6 7" is more for the side buttons and you need to add on a few other programs for that to work.