Fedora Core 2 on a Dell Inspiron 8600
Monitor Out (Dual Desktops).
Getting dual monitors working took a bit more work than I would have expected. The key eventually turned out to be setting the Option "ConnectedMonitor" "DFP-0" and Option "ConnectedMonitor" "CRT-0" in the respective devices. These refer to the laptop's flat panel display and the connected CRT monitor respectively. There was a lot of trial and error involved as well as some debugging so it may not be the only factor.
I had read reports of poor performance but once up and running performance seems quite good. UT2004 demo still runs at a playable rate. The only other niggles are the second display comes up with the default settings except for the desktop background and the Gnome logout dialog doesn't appear you are simply logged out when it is selected.
Whenever you are editing key system files you should make a backup copy. In this instance I suggest you make two copies. One in /etc/X11/, as say xorg.conf.bak, that can be restored if need be. The other in your home drive in case it takes numerous attempts and you overwrite your original configuration.
To get Monitor Out running you need to set two device, monitor and screen configurations in xorg.conf. Screen 0 will be your current flat panel settings. Screen 1 will be for a connected CRT screen. The ServerLayout section then needs references to both screens and their relationship to each other. That is, do you want the second display to the right or left of the main display? If to the right, move the cursor to the right edge of the main display to move it onto the second desktop.
It is possibly to use more descriptive names than the defaults in xorg.conf file. The naming needs to be consistent for each screen as the screen, monitor and device sections reference each other. A copy of the conf file I created for Monitor Out can be found here.
The CRT monitor does not show any details when booting but it switches power mode so you will no something is happening. Once Gnome has loaded and the desktop displays then the second monitor starts up. The monitor can also be plugged in after the laptop has been booted.