Hacer un preloader en CS3

 
/************************************************************************
Preloader by http://www.TheCosmonaut.com
Modified from source code from Chris Sessions
Preloader movie clip must have 100 frames
************************************************************************/
//-- stop the parent movie
this._parent.stop();
//-- Define the name of the start frame. You can change this to be anything (a frame number or a frame name). Whatever it is, it refers to the frame of the main movie clip you want to play when the preloader is finished preloading.
var startFrame = "main";
//-- preload function
var preloadCounter:Boolean = false;
function preload(cutoffPercent:Number) {
    var totalBytes:Number = 0;
    var loadedBytes:Number = 0;
    //-- add parent bytes to total  
    totalBytes += Math.round(this._parent.getBytesTotal()/1024);
    loadedBytes += Math.round(this._parent.getBytesLoaded()/1024);
    //-- calculate percent done
    var percentDone = Math.round((loadedBytes/totalBytes)*cutoffPercent);
    if (loadedBytes>=totalBytes) {
        if (preloadCounter == false) {
            percentDone = 0;
            preloadCounter = true;
        } else {
            this.stop();
            delete(this.onEnterFrame);
            this._parent.gotoAndPlay(startFrame);
        }
    } else {
        this.gotoAndStop(percentDone);
    }
}
//-- start the function
this.onEnterFrame = function() {
    preload(100);
};