I would think that it was supposed to go to paypal... then the success page... then have a link to the download center on the success page.
For that though you need to have login working. So back to that... do you have a login page that works?
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.