I have had similar problems in the past. I used a bit that is smaller than the screw to carefully drill into the screw and destroy it. Make sure it is placed in the center of the screw and go slowly so you don't damage the cabinet. Wear gloves and goggles in case the bit breaks. If it is not too badly striped you can also try to improve the grip by using an old slot head screw driver and hammer. You hold the screw driver at an angle and gently tap it with a hammer from one end of the head to the other. Do this a few times to create a new slot. Sorry it is very hard to describe how to do this without showing you. If it is very hard to loosen the screw you should very slightly tighten it first as this helps unseize it. Good luck.