how do I get a Virtual Desktop ( larger than actual screen ) in Ubuntu ?

I have a small 19 Inch moniter, and bad eyesight.
I want a Virtual Desktop Screen,
a screen that is larger thatn the actual moniter screen.
In other versions of Linux I would edit the
         /etc/X11/xorg.conf
to look something like this ....
--------------------------------------------------------------------------
...
Section "Screen"
    Identifier "Screen 1"
    Device "** NVIDIA (generic) [nv]"
    Monitor "My Monitor"
    DefaultDepth 24

    Subsection "Display"
        Depth 8
        Modes "640x480"
        ViewPort 0 0
        Virtual 1600 1280
    EndSubsection
    Subsection "Display"
        Depth 16
        Modes "640x480"
        ViewPort 0 0
        Virtual 1280 1024
    EndSubsection
    Subsection "Display"
        Depth 24
        Modes "640x480"
        ViewPort 0 0
        Virtual 1152 900
   EndSubsection
EndSection
...
-------------------------------------------------------------
In other Linux Distributions this would give me
a Virtual Screen ( larger than the actual moniter screen ).
Not In Ubuntu.
When I edit the xorg.conf file in Ubuntu
and put values similar to this in it ,
I don't get a virtual screen.
My question is How do I get a Virtual Screen in Ubuntu ?
I am an experienced Linux user,
If you give me detailed instructions, I can follow them.
Thank You.