The drive on my macbook 13inch (white) failed so i bought another one. My drive has a model number of "combo 8221a 678-0567a". I replace it with a "8221a 678-0567g". I cant get the superdrive to line up when i put a cd in. The laptop recognizes the drive and it works nicely when i have it all taken apart for testing. Will this drive fit my macbook 13inch? Does the "g" make a difference? they look almost identical but i cant get it to line up with the slot on the side of the computer.