Digital download shopping cart mod

Company overview... One man band, selling licensed MIDI files and MP3's. Current website.. ASP based shopping cart mainly coded by myself, run off 3 seperate Access databases, 1 for MIDI files, 1 for MP3's and another for offline transactions (Tracks transferred to CD or Minidisc) sent via post. My cart doesn't currently include a payment processing system. (OK for CD's and Minidiscs, because if the card is bad the item doesn't get sent). But regarding the downloadable files, the tracks gets added to the cart, card is checked by a basic asp card vaildation code and once submitted the customer is sent to a URL with links to download. I then receive an email and process the card offline, generally after the customer has downloaded the tracks. NOT VERY SECURE AT ALL. But I must admit I haven't had too much problem with this. I have recently tried to incorporate a credits system where the customer buys credits (per file). I have a dll which allows me to place the purchasable files into a non public folder. This also recognises the extension (.mid, .mp3). The client can then download until credits have expired. Solution needed.. I would like to integrate my 3 databases into one. Incorporate a payment system for purchasing credits and on validation parse the info back to the database. Paypal will be fine for starters, but may like to change to a more UK based system in the future. I can supply my current cart for an idea of the current look and facilities that are already implemented and will be need to be kept eg. lost passwords, sign in, wishlist. My administration section will also need to be recoded, so i know what client has ordered what items on completion of credit use per order. I would like a complete new look and design on your recommendations and ideas. My current cart code is quite messy but gives you an idea on what currently works and gives you ideas on how to improve. ## Deliverables Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. Complete copyrights to all work purchased. ## Platform I use IIS5 and perl. My hosting company does allow registration of private DLL's. I also have my own SSL cert.