If you are using an ATI graphics card with Linux then you might be struggling with the fact they have helpfully decided to only use two thirds of your screen.
They actually do the same thing with windows but give you a nice tick box to disable this “feature”
In linux though we are not so luck and the GUI admin tool simply does not have the corresponding tick box
here is your solution
Inspiration and credit goes to this thread on the Ubuntu forums, I just scripted it to make it easy