ebshop with 1 product, 1 download and a productregistration module

Dear programmer, We want to have a webshop with one product. (Expecting more product in the future) Right now we have prestashop installed on a wordpress installation. Not finished, so let me know if you prefer a different webshop software. The product is a downloadable software or sent as an installation CD. Steps to buy: Klik: buy now button on another site -> goes to webshop. Mandatory create a customer account: Name, email, phone, username, password After submit, customer is logged in. Now they can order either download or CD. Extra costs when CD. Pay by Ideal. After payment redirect to downloadpage or to send CD redirect to page with both donwload link and postal address fields. Product registration module Customer gets a serial numer. He/she logs into website with username and password. Sees his profile-page. Possibilty to enter more fields: affiliate(checkbox), mobile phone, private address. Button: Register your version! When customer clicks, a page (or pop up) opens. His serial number has to be filled in this field. Click submit. Software makes a calculation: - Serial number / 5 = Result - Result + 5 = Result - Result - 5 = Result - Result * 5 = Result - Result - 5 = Result - Last 6 number of Result is unlock code Unlock code is shown on the screen and saved together with serial numver in customer profile. Admin has to have future option to change the calculation. If user tries to click on Register your version, he gets a message: you are already registered with a serial number. The customer can view his serial number and unlock code in his account. No changes possible in one of those numbers. Deadline is April 25th!