My Toshiba Satellite E45-B4100
has lost 3 screws. Two of which hold the battery in place! It fell out and hit the ground today. Wasn't sure if it was just me or Toshiba's fault. Well, I also kept my old Toshiba laptop which was also missing three screws in the back! So my Satellite C55Dt-A5106 is now down six screws! They fit in my new-ish laptop! It's only 3 or four years old. And I keep it in my backpack using it multiple times a day so I guess that's enough to have them losten up. As for the screw size I couldn't tell ya. I'd just recommend tightening them all periodically!