I have an older MacBook and when I bought it, from a friend, it already had windows running on it. Just the other day I went to restart my computer and all I got want the black screen saying that the computer was turned off wrong and to choose the start up mode. I tried the last known option and nothing happened besides restarting to the same screen. Then I tried the normal mode and that didn't work and safe mode did the same thing, starting back up to the black screen. Is there something that I can do/fix, or does this require some professional help? Thanks!