And don't forget if your a smoker, they'll likely tell you it's contaminated and they cannot repair it. lol
But in a more serious manor, what do you mean the cpu display doesn't turn on? A cpu is a chip inside the computer, are you saying your monitor doesn't turn on anymore? If that is the case sounds like a video card problem, but I really can't offer much help beyond that, never owned a mac and never intend to.