I've been using this macbook pro for awhile now but never had this problem! Before I turned on the macbook, my external hard drive was connected to it. So I disconnected it and then pushed the power button on. then the screen loads to a gray color with apple logo and spinning thing below it, and stays like that for a very long time and wouldn't start-up. So I held the power button off, and the second time before I turned my macbook on, I reconnected the external hard drive (the same one) to it. it starts up the same way with the gray screen for a long time, so I disconnected my external hard drive while it was still showing the gray screen, and surprisingly the screen moved to a blank blue screen this time. I see only my mouse and nothing else, so it leaves me confused and very frustrated. anyone know what's the problem? would help me A LOT. thanks in advance.