Use xrandr to find your monitor names then xrandr --output MONITORNAME --primary
Then add that as a command to your System->preferences->Startup menu.
Reference: http://ubuntuforums.org/showthread.php?p=9489366
There should be a tickbox on the Monitor Preferences dialog along with the monitors to set the primary monitor.
Use xrandr to find your monitor names then xrandr --output MONITORNAME --primary
Then add that as a command to your System- >preferences- >Startup menu.
Reference: http:// ubuntuforums. org/showthread. php?p=9489366
There should be a tickbox on the Monitor Preferences dialog along with the monitors to set the primary monitor.