I'm with BDgrepory. If you can get all of the other screws out, you can usually lift the other edges of the cover up a bit, then turn the entire cover. It will generally move the stuck screw a bit an loosen it up enough that you can remove it.
Just be cafeful not to lift the cover too much and bend it. It only has to be lifted enough to clear any edges that may stick up. If there is nothing sticking up past the top cover, you don't need to lift it at all, just turn it on the axis of the remaining screw.
Another thing you can try is to use a very small flat blade screwdriver that is not as wide as the head of the screw. Place it in the center of the screw and give it a few firm taps with a hammer. It will generally cut enough of a slot into the screw head that you can get enough bite to get the screw started.
Enjoy,
TIC
Enjoy,
TIC
Just be cafeful not to lift the cover too much and bend it. It only has to be lifted enough to clear any edges that may stick up. If there is nothing sticking up past the top cover, you don't need to lift it at all, just turn it on the axis of the remaining screw.
Another thing you can try is to use a very small flat blade screwdriver that is not as wide as the head of the screw. Place it in the center of the screw and give it a few firm taps with a hammer. It will generally cut enough of a slot into the screw head that you can get enough bite to get the screw started.
Enjoy,
TIC
Enjoy,
TIC