The laptop ships with Intel Graphics Media Accelerator 900, and I’m using this display controller:
kenneho@laptop:~$ lspci |grep Display
00:02.1 Display controller: Intel Corporation Mobile 915GM/GMS/910GML Express Graphics Controller (rev 04)
My external monitor is running with a 1280×1024 resolution, and are placed on the left hand side of the laptop.
I tried configuring the dual monitor setup using xrandr as were suggested on many linux forums, but didn’t quite get it to work properly. But instead of using xrandr, I found that I can easily set this up using Xfconf which is already installed. By simply clicking “Menu” > “Settings” > “Settings Editor” to enter the xfconf graphical adjustment interface. In there I clicked “display” > “Default” and then my laptop display (in my case “LVSD1”). From there I clicked position, and entered “1280” into the X variable. In other words, I say to linux that the laptop screen should start at where the external monitor screen ends (vertically).
Then, after a restart of the X server (log out and log in), everthing worked just fine.
Update 2011-07-01: I currently have an issue with running different screen resolutions on the two monitors; when running with different screen resolutions applications such as Firefox are “dimmed” so to speak, where the application window becomes very dark/grey. I’m looking into how this can be resolved.
Update 2011-09-26: In the first posting in the comments section below, Pedro Rainho provided a solution that fixed the issue I had. If you have the same issue as I had, you may want to apply the fix he suggested. Thanks to Pedro for providing the fix.