Linux noob here...trying to getFedora 15 + LXDE + Desktop extended over 2 displays...No luck...I have an extra CRT plugged in to the VGA output of my laptop but it only displays in mirrored mode(even if I disable the mirror displays option).
Does your laptop has a dedicated graphics processor (mine has a mobile nVidia chip). If so, you might need to install the driver for it. I know that on my desktop I don't get multiple monitors to show up until I install the graphics driver.
I'm busy reading through those links now...But what is funny is that I plugged in my laptop and booted up and the extended desktop was suddenly working..the only problem is that it made the CRT the primary display and I couldn't figure out where to change it...But after I rebooted again it went back to the same behaviour of mirroring the displays...