hinge security

I couldnt find this in the sticky. First of all I realize that making a TT really secure is somewhat impossible, and if someone wants in badly enough, they can pry a wall off or go through with an axe or anything else crazy. I want to install my hinges so that they cannot be unscrewed from the outside. On my door for example, they will only be accessible when its open. I noticed some are exposed... For my windows though, its not going to work, and I think the screws will ahve to be exposed. I am thinking of two things... first, putting an extra latch inside mathcing the one that holds windo closed at the bottom, but at the top also, so even with no hinges it would stay put somewhat. Also, I was thinking of welding the screw heads in place to the hinge. I wouldnt over do it, but just enough to make it impossible for the casual theif or mischevious kid to undo, but not too much i couldnt grind it off if I ever needed to remove it. Has anybody ever tried this or have any suggestions?
-Will
-Will