What you're looking for is a screen-sharing or webconferencing tool. I work for Glance Networks, where we produce Glance, a program designed exactly for the kind of situation you're describing. You set up a Glance account, which gives you "yourname.glance.net". Then, when you need to do a product demonstration, you provide your customers (up to 100 at a time) with a randomly generated 4 digit session key that they enter on your glance.net page. They are then shown exactly whats happening on your screen. It's very effective, simple, and dependable. Check us out!