mint12- turn off screen dim

[bmike1]

I have linux mint 12 (maya) on an ancient computer (IBM NetVista) upon which I have loaded XBMC (mint12 because it is the last cd edition). After some time the screen dims. How do I turn that feature off? In my search for the solution all I found is what I tried: system settings->screen. Unfortunately all that is under that setting is "Turn off after:" So is there a way to do it? It seems there is a way to do in with Cinnamon. So please, teach me! Will I have to reinstall with cinamon. If so is there a way to merely downgrade?