Ciao, prova così
codice:
var loader:Loader = new Loader();;
 loader.load(new URLRequest("main.swf"))
 loader.contentLoaderInfo.addEventListener(Event.COMPLETE, onLoaded, false, 0, true)
function onLoaded(evt:Event):void{
addChild(loader)
evt.target.removeEventListener(Event.COMPLETE, onLoaded)
loader.x = 100;
loader.y = 100;
loader.width = 350
loader.height = 200
}