the head of the screw protrudes beyond the handle: Get a hax saw and carefully cut a straight long cut into the head. Make the cut as deep as you can. Then get a screw driver with the sloted head, and then make sure it fits deep into the groove. If not, make the groove wider or file the head of the driver where its at more of an angle.
Now, carefully apply alot of downward pressure on the head of the screw driver and at the same time turn. If you bounce up and out of the slot, you may waller the groove and cause more problems.