I have got a 13 inch MacBook Pro and it got stuck in a loop so I switched it off by holding the power button down and now when I switch it on the apple logo appears then I get a blank slot at the bottom of the screen then the circle appears and rotates and then it switches off again, I have tried starting it again with the system disc that came with it when it was new but it makes no difference. Is there a sequence that I can use to force it to start.
MacBook Pro with Retina display, iOS 6.1.4