Index Server is a free Microsoft product that can be used to Index the content on your Web server. Once your content (Word files, HTML pages, text files, etc.) is indexed, it can be queried using ADO. If you need your Web site to be searchable, an easy and powerful technique is to use Index Server.
Unfortunately the documentation for Index Server is painfully lacking. While there are some samples that accompany Index Server, solid documentation is sadly lacking. To learn more about Index Server you must turn to the Web or books. Here are some great links to help you get started learning more about Index Server!
Index Server Information
Index Server Examples
Index Server Tips & Tricks