Originally Posted by icemilkcoffee

Don't do any of the things other people told you to do here. Here is what you do - Take the other screw off. Now rotate the entire caliper counter-clockwise around the stuck bolt. All you need to do is swing it outwards roughly 30 degrees. That will expose the 2 caliper mounting screws under the adapter piece. Loosen those two screws and remove the caliper from the adapter. Now you can go to town with the adapter and the stuck screw.