This is a simple guestbook lesson/example that consists of 3 parts: Display for showing the content of the guestbook file, Form that visitors can add their greeting, and Write that adds the greeting to the guestbook file. The code is pretty easy and well commented.
If you want to add a guest book to your site, then this article is for you - it contains full source code and the necessary Access database to get up and running immediately. A complete introduction to ADO is provided.