Great, Danny22, but maybe he's using AS2 since he mentioned this: Stage.scaleMode = "showAll";

It's a bit different in AS2, but the concept is the same:

Actionscript Code:
Stage.scaleMode = "noScale";
Stage.align = "TL";

resizeListener = new Object();
resizeListener.onResize = function(){
    // example code, this will align
    // a movieclip to the center of your Flash
    mc._x = Stage.width/2;
    mc._y = Stage.height/2;
}
Stage.addListener(resizeListener);

There was a good tutorial in AS2 for this as well, but it was deleted recently