from what you describe, it sounds like the engine has seized up, take the head off and see if you can move the piston, with luck the piston will be near the top of the cylinder so you can put a piece of timber on top of the piston and hit that with a hammer until the piston moves, then with the piston free you'll be able to remove the barrel, chances are you'll need a rebore and new piston and rings anyway, depends how badly scored the cylinder is, then find out why it seized before its run again.
Perry
February 2013