Hi,
I have been rooting around with this for ages, trying to setup Ubuntu & Mythtv using Dual Monitors (LCD TV & Monitor) connected via DVI-HDMI & VGA.
I tried editing xorg.conf manually, then tried using xorg-edit, where I got closer, but all this time the answer was right under my nose. Just install the nVidia Beta Driver below....DOH!!!
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How to install Beta Graphics Driver (NVIDIA)
* Thanks to Alberto Milone
* Read #How to add extra repositories
sudo gedit /etc/apt/sources.list
* Add ONE of the following lines based on your architecture
deb http://www.albertomilone.com/drivers/edgy/latest/32bit binary/
or
deb http://www.albertomilone.com/drivers/edgy/latest/64bit binary/
* Save the edited file
* Add the GPG key
wget http://albertomilone.com/drivers/tseliot.asc
gpg --import tseliot.asc
gpg --export --armor albertomilone@alice.it | sudo apt-key add -
* Update and install
sudo apt-get update
sudo apt-get install nvidia-glx
sudo apt-get upgrade
* The upgrade should update your linux-restricted-modules & linux-restricted-modules-common packages.
sudo nvidia-xconfig
* Add a menu option for nVidia Settings
sudo gedit /usr/share/applications/NVIDIA-Settings.desktop
* Insert these lines in the new file and save
[Desktop Entry]
Name=NVIDIA Settings
Comment=NVIDIA Settings
Exec=nvidia-settings
Icon=
Terminal=false
Type=Application
Categories=Application;System;
* Restart the computer and your new drivers should be installed.
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You then need to login as root after the restart. Look in Applications>System Tools - NVIDIA Settings and you will see the attached screenshot!
Hope this saves some one else

Lester