ICT network administrator
@Lorenzo, via YouTube with these headwords, you ‘ll find a few video’s that guide you with replacing the thermal paste. Success and let us know how it worked: macbook core 2 duo thermal paste
Olivia, you can screw back the longer screws that go on the inside. In the photo marked with orange. Then open and close the lid of the MacBook a few times. This will fit the 4 screws more properly in the steel inner-frame and they can come a little bit loose.
Close the lid again. Leave the inner screws untouched and begin with the outer screws (marked with red) with indeed a perfect matching screwdriver head (with a big and long grip for your hand). This worked for me perfectly without damage. Success!
With some of the screws that can happen. I had it too. This did it for the MacBook I was repairing: 1. Open the MacBook. Then press firm but gentle on the upper case with your hand or fingers while trying to loosen the screw with your screwdriver. 2. I used a different screwdriver from the same size diameter but with a much larger hand-grip. Success!