Dirk.Net

You’ve surely read this article on the topic, which describes a long (and arduous) process to set up dual monitors on an Ubuntu system with a lowly graphics chip such as the Intel 945GM.

However, there is a much easier option which is outlined here: 

For my system, all I had to was add the bold line in /etc/X11/xorg.conf

Section "Screen"
	Identifier	"Default Screen"
	Device		"Intel Corporation Mobile 945GM/GMS, 943/940GML Express Integrated Graphics Controller"
	Monitor		"Generic Monitor"
	DefaultDepth	24
	SubSection "Display"
		Modes		"1280x800"
Virtual                 2048 2048
	EndSubSection
EndSection

I then “activate” the secondary monitor with the command:

xrandr –output LVDS –below VGA

There is a 2048 pixel limit for the height and the width of the total display. For me that’s no problem as I have a vertical setup (secondary screen ABOVE notebook screen), but your mileage may vary if you need the screens side-by-side.