I have a 17" Late 2011 MBP. I had a clean updated install of Mavericks on the HDD and a Superdrive also in the computer. I successfully ran Boot Camp to install Windows 8.1 on the HDD. I was able to boot between the Windows and Mac partitions. I then opened up the machine, moved the HDD to the superdrive slot, and put in my SSD that has a Macintosh install that I had previously used with this computer. As in, before I put the HDD in the computer, I had this SSD in, and I haven't deleted anything from it. Theoretically I should be able to boot to that SSD. The problem is that now my computer starts but the screen is black. It seems to be completely working as in (1) I hear the start chime (2) the keyboard backlight turns on and is responsive to keyboard commands (3) the caps lock key lights on/off when pressed (4) When its on and I press the power button it makes the normal Mac OS honks at me (5) when I press other buttons it also honks at me as if I'm in a menu and doing the wrong thing. Its just the the screen went dark. I really don't think I broke anything while I was in the computer. Everything seems to be attached. I have reset PRAM and that didn't seem to do anything. I have tried to reset SMC although I don't know how I'd know if that was successful. I have also held down shift and the power button at the same time, which supposedly boots into safe mode, but I don't know if that is working. If it is it isn't helping my black screen situation. Any ideas?