Unable to enable dual displays

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http://askubuntu.com – I am running an almost-fresh version of Ubuntu 12.04 on my old Dell Inspiron 710m laptop. I had to re-install yesterday due to a different display issue. I wasn't able to directly reinstall 12.04 because my system can't handle the PAE kernel. Instead I installed Xubuntu 12.04 and then installed the Ubuntu desktop. Now I am unable to enable my dual displays. I want to use the laptop screen and an Asus VE228D monitor attached to the VGA port. Ubuntu sees both of them (both via xrandr, below and Displays). I can set both to 'on' in displays, but when I hit Apply, only one shows the desktop (the (HowTos)