Also, I don't see this as it, but always check the easiest stuff first, even if it is less likely. That is, check the ribbon cable to the HD and reseat it. It know of several instances where that fixed what was thought to be a HD failure.
I had a ribbon cable come undone but only on one side so I reversed it so the damaged side is connected to the motherboard until I can get a new one just so I can still change out the HD if I want to.