One of the changes on the new Ubuntu 9.10 is that xorg.conf is missing. The reason for this is that the configuration to be done on user level. The file xorg.conf will be in use only if it exists. Only the time will show if this new concept is good but I personally thing it is.
Sometimes you do need to have the xorg.conf though. Mainly when you need to use some hidden options of your graphic device or touchpad for example.
Firstly we need to create the file xorg.conf. Fortunately there is automatic way of doing this with generating xorg.conf with the detected devices from the X.
In order to generate xorg.conf you need to switch to one virtual console using the key combination CTRL + ALT + F1.
Now execute the following commands:
user@ubuntu ~# sudo service gdm stop
This command will stop the X.
Now we need to generate the xorg.conf file:
user@ubuntu ~# sudo Xorg -configure
This has generated the file in ~/xorg.conf.new.
We need to make the X using it so we have to put this file inside /etc/X11/
user@ubuntu ~# sudo mv ~/xorg.conf.new /etc/X11/xorg.conf
After moving this file to the proper location you can start the X again and see what happens:
user@ubuntu ~# sudo service gdm start