I have an Nvidia video card. To get the most appropriate driver I will install and run EnvyNG-gtk, which can be downloaded via the Synaptic Package Manager. Once it''s installed, running it is a snap! Applications -> System Tools -> EnvyNG

I selected "Automatic Hardware Detection", then Apply.


Immediately after selecting apply the following window popped up. Once the operation was complete I confirmed and closed the application.


Now I can attempt to get my dual monitors working by using the Nvidia GUI. The previous operation installed the Nvidia X Server Settings tool which can be accessed at Administration -> NVIDIA Server Settings.

At this screen select X Server Display Configuration


At this screen select the "[Disabled]" monitor on the right, then select Configure below.


I prefer to have my screen extended over two monitors, so I chose "TwinView". Selecting "Seperate X screen" will result in a menu bar on each screen. In "Seperate X screen" one will not have the ability of dragging items from one screen to the other. I recommend "TwinView", then select "OK".


At this stage you should save the settings to the Xorg.conf file by selecting "Save to X Configuration File".


As shown below, select "Merge with existing file" and Save


The reason I have an error, "Unable to remove old X config backup file ''/etc/X11/xorg.conf.backup'', is because I can''t save the xorg.conf file unless I am in super user mode.



Thus, one should not launch the NVIDIA Server Settings application from Administration menu. Instead it the NVIDIA Server application should be opened using sudo in the terminal:

• $ sudo nvidia-settings
  

From the sudo command in the terminal the NVIDIA Server Settings application will launch in sudo mode. One can now follow the instructions as mentioned above, but this time there will be no error when saving to the xorg.conf file.