Finally decided to buy a new screen for my cracked iPhone 4S, and getting to the last parts of the process of removing the old screen. In the four corners of the phone are tiny little Phillips Head screws. I removed three, but there's one that won't come out at all. I can see the screw turning, but I've been trying for the past 10 minutes to try and get it out, but nothing. Any tips or tricks to get it out?