Make a window target

var self:DisplayObject = this;
this.addEventListener(MouseEvent.MOUSE_DOWN, function(event:Event):void{
     if(event.target == self){
	self.startDrag();
	self.addEventListener(MouseEvent.MOUSE_UP, function(event:Event):void{
	     self.removeEventListener(MouseEvent.MOUSE_UP, arguments.callee);
	     self.stopDrag();
	});
      }
});