We have an older G4 in my office and it dropped about 2-3 inches on the rear portion when my co-worker was trying to seat it back under the desk. It immediately started making a clicking noise. It's reminiscent of the sound a CD makes when skipping. I checked the optical drive, but that seems fine. I know someone here has way more knowledge on this than myself. Can you guide me as to what I should be checking when opening the system? I have a G5 tower at home and hadn't seen the inside of a G4 before. Thanks for any advice!