I replaced the bottom case of my macbook pro with a new one I ordered off ebay. I followed the instructions from iFixit.com very meticulously and thought I had everything right upon completion. But when I hit the power button all the computer did was illuminate the sleep light and make a faint whirring noise (not as loud as it normally does). Does anyone have an idea of what I might have done wrong? I know there's probably a million things that could have gone wrong, but I am just seeing if anyone has any past experience with the same thing.