To remove the 4th screw hidden by the DVD drive bay, one needs to remove the DVD back plate. To do so first remove the angled DVD black plastic door (the one with the open button) to free the DVD back plate. Next put the computer face down. This is important to ensure the DVD catch and spring stay in place. Next remove the DVD back plate by removing the screws first and then pop and slide the back plate out. There is no need to remove the 2x front plates. Next slide the DVD door in and out until the 4th screw is revealed. The screw can now be removed through the DVD drive. I agree with Mark: I also left the 4th screw out when re-assembling as the whole procedure is quite time consuming just to take 1 screw out. Leaving the 4th screw out, reassemble the DVD back plate and leave the DVD plastic door until last once the PC is re-assembled.