i have a 2012 macbook pro running latest osx. in order to give a presentation to parents at school i booted the computer while connected to an lcd projector with a different resolution (800 x 600, i think) than the macbook. now, whenever i boot the macbook it has black letterboxes on either side of the screen. the first time i booted it after the presentation i had to switch the resolution back to 1680 x 1050. once the computer gets past the apple logo and that circular rotating dash thing, it reverts to 1680 x 1050 and the letterboxes go away, but for some reason it bugs me. is there a way to stop it from doing this? thank you for your time!