Secure Download after PayPal Payment

I need an ASP page that will allow a software title to be downloaded after someone pays via PayPal and I want the URL to be hidden somehow. I had this previously done but it really ticked off the buyers when it didn't work. I need a way to test the page also upon completion. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform Windows 2000 Server IIS