[Бармалей]

а еще лучше:

if (sound.getBytesLoaded() < sound.getBytesTotal()) {
player_mc.preloader_mc.mask_mc._width = proc;
}
if (sound.getBytesLoaded() == sound.getBytesTotal()) {
clearInterval(time);
sound.start();
player_mc.preloader_mc.visible = false;
player_mc.play_mc._visible = true;
}