Even very talented developers have issues getting Ubuntu to work with a projector to give a presentation using a laptop. I know I had problems getting it to work, too, and I am giving a demo using Ubuntu to my class this week. So here are the settings I used which do work:
I have an Nvidia video card, so I’m not sure if this will work for an ATI card. I added these lines under the ‘Section “Screen”‘ in my /etc/X11/xorg.conf file:
Option "RenderAccel" "true" Option "TwinView" Option "MetaModes" "1680x1050 1680x1050" ####Change above to your screen resolution Option "TwinViewOrientation" "Clone" ####Above option can be: LeftOf, RightOf #### Below, Above, or Clone
Be sure to backup that file before editing it. If you have an error when you reboot your computer or restart gnome (control-alt-backspace), you can hit control-alt-F1 to go to a command line login to your system, where you can restore the original xorg.conf file.
There is an nvidia-settings tool you can install which provides a graphical way to do this, but I found it messed up my system because I am using the nvidia-glx-new driver, not nvidia-glx. It does work fine though as long as I don’t do anything that causes it to reinstall drivers.