Re: Single page and single product shopping cart.
Honest opinion? As much as we would love it if you used Zen Cart - Zen is MUCH more than you need and will need modifications to meet your needs.
I am looking to have a single page system that already has a product in the cart and where the user can ( as a guest and without registering ) can fill out there shipping and billing information and purchase the product. I will be using "buy now" links for my advertising so I do not want them to have to go through the registration process or a two+ step process for checking out.
Please do not PM for support issues: a private solution doesn't benefit the community.
Be careful with unsolicited advice via email or PM - Make sure the person you are talking to is a reliable source.