I'm attempting to install Windows on my Macbook and I got to the point where it asks for my product key. I've put it in several times and it continues to tell me it's invalid. This is an authentic copy of Windows 7 Professional. Now I'm stuck at that screen. How do I go about getting back to OSX? How do I eject the disc? I don't mind giving up on Windows (have an old Windows laptop laying around). Edit: Got it rebooted into OSX. Anybody have any idea why it won't accept my product key?