Strange as it looks like it should work. Can you confirm that the screwdriver makes proper contact with the screw heads? The only thing I can guess is that somewhere along the line non-standard screws were used similar to either Torx heads or the screws were over torqued when tightened.
  Greetings , i've been trying to upgrade my dell optiplex 790MT from an i3 to an i7, but can't manage to unscrew the heatsink off the motherboard I tried first both screwdrivers PZ 1X100mm and pz2 X100 mm with no results. I then bought Philips screwdrivers P1 and P 00, but i'm facing the same issue the screws wont move at all... am i doing something wrong?  Does anyone know which screwdriver model exaclly i should use to remove the scews from my heatsink please?  Kind regards
Help unscrewing optiplex 790MT heatsink