I am trying to make an ecommerce website just to sell a few digital mp3 files for downlooad. What i want is for people to buy the mp3 through paypal...and after payment is sent and received then i can send the download via email to the verified email of the buyer. I want the delivery of the digital mp3 to be automatic..done in the script...as long as payment if verified then download is delivered to email.

What is the simples ecommerce free open source software/template to help me do this? I can customize the thing myself as i am good with php/mysql..just want to start out from an open source script.