Hi! I would open it up again and double-check that the rubber rings that go around each of the four hard drive screws are in place, and that they have not come off or been pushed aside. These act as shock absorbers within the computer, keeping computer movement from affective the drive, and drive movement from affecting the computer. If for whatever reason one of them is not in place, then likely the metal of the hard drive is directly touching the metal of the computer, causing vibrations.