Oh, so when you put the allen wrench in it just spins without moving the screw?
Just go to a hardware store and get a new screw. As for removing it...that is really tricky.
If you can, i would suggest buying a specialized kit for removing stripped allen screws.
If you don't want to do that you can try either using a larger allen wrench or a Philips head screwdriver.
If neither of those work you can dip super glue on your allen wrench and let it stick to the screw. However i don't suggest this because if you get glue in your threads....well yeah, thats not good.
82nd Airborne Pathfinders, D-Day: 2010-13
Georgia Tech Yellow Jackets, NCPA: 2010-13