13.04 Dual monitors on my desktop
I got it to work
Here was my fix. (sorry i do not have images, I do not know how yet) 1. Go to software updater and click on "settings" then select the "additional drivers" tab. Make sure the correct driver in selected...On my computer it is "X.org X server..." driver.
Go to "Ubuntu Software Center" type "xorg" in the search bar and install the "NVidia binary X.Org driver"
Go back to display and deselect the mirror option and it should work.
Additionally when I was using 12.04 I followed step 1 above but for step 2 would have to install the "ATI binary X.Org driver" found by typing "ATI" into the softwear center and then step 3. would to search applications by typing "amd" and tweaking the amd catalyst settings.
I hope that this helps, it worked for me.
Try running arandr. It's got settings for multiple monitors, mirroring or not, etc. It's in the repos.
sudo apt-get install arandr