ActionScript 3.0 :: Unload Previously Loaded Clips?

I am creating a 40 slide presentation with soundtracks, narration, and animations.Each slide is a separate swf clip).I have noticed that when I load a new clip, the previous clip is still loaded (I wasn't using any background so I could see through the first clip and see the second).This tells me that I should consider unloading the previous clip or use backgrounds.Putting on a background is easy however if I should want to unload the previous clip, how do I do that?Here is how I load the next clip:

mmBtn.addEventListener(MouseEvent.CLICK,loadMM);function loadMM(event:MouseEvent):void {trace("Main Menu Button was Pressed")var loadMain:Loader;loadMain = new Loader();addChild(loadMain);loadMain.load(new URLRequest("mainMenu.swf")); }

Some slides will have many navigation options and others will only have one or two.I have AS in each slide to keep each slide self contained. This makes it easier for me to develop and test.Is there a way to remove the current slide contents (from the stage and memory) and load the next slide? I'm really concerned about the memory usage.