There's a slider in the ati control panel that makes your displayed screen size bigger or smaller, can't remember what it's called, it's somewhere in the 'display' options
quick edit: I got this a couple days ago and the picture seems kind of fuzzy, I've got the colours and contrast etc set up, the edges where different colours meet just seem to blend into one another a bit and it's giving me a headache, any idea what it is?