Replay Button for Flash Movie

First, create your play button. Click on it, and open up the Properties Panel (Shift + F3). Type in: play_btn for the <Instance Name>.

Then, create a new Layer in your Flash file, called Actions. Click on the first frame of the Actions layer, and open up the Actions panel (F9).
Type in:

stop();
play_btn.onRelease = function(){
play();
}