PHP Website maintained thru Windows Software Program

We will be developing cookie-cutter websites for customers and they will be updating them using the "windows program" you develop. Basically, there are Update Forms on a website that are coded in PHP. We want to have users make the changes from their local box. The product looks and installs exactly like any other Windows XP Program. I have provided a mock-up screenshot of the finished "windows program" desired. (project may not necessairly be as involved as the screenshot provided). I want the ability to assign a unique URL, login and password (unseen by user) to each software copy from me (the manufacturer) to the consumer.