Macbook Pro 15 inch mid 2010 - 4gb - 500gb - running OS X Yosemite Okay. I've tried resetting the NVRAM multiple times. I've also reset the SMC several times as well. I was using my Macbook Pro like usual when all of a sudden it shut down. After that, I've been unable to successfully boot the machine. Sometimes it will try but will never actually make it to the desktop. Even when I boot using the ALT/Option key, it will sit on that screen for several minutes sometimes and then shut off again, usually just the screen goes black. And no, I can't see any data when I shine a light on the screen. The furthest I've got is to disk utility where I was able to "unlock" my hard drive and begin a repair. It shut down before the repair could complete. What is this? An HDD problem or something worse? Thanks for any help!