Drag and drop con Flash

Código Flash

on (press) {
	var xcor = _root.AAA._x;
	var ycor = _root.AAA._y;
	startDrag ("_root.AAA");
}
on (release) {
	stopDrag ();
	if (_root.AAA._droptarget == "/BBB") {
		_root.AAA._x = _root.BBB._x;
		_root.AAA._y = _root.BBB._y;
	} else {
		_root.AAA._x = xcor;
		_root.AAA._y = ycor;
	}
}

AAA = Instance name for the movie clip that is to be dragged
BBB = Instance name for the movie clip that is to be dropped on it
Brief Explanation:
AAA consists of a "button". And, the action of this button has to be like above. Also, pay attention that the center of AAA and the center of the button has to be matched.