Holy cow, I wrote a book!
If you double-click a file for which there is no registered handler,
Windows will offer to visit the Web service on
shell.windows.com to locate a program that can open it.
But where does this information come from,
and how can you add your program to the database?
Knowledge Base article Q929149,
titled Windows File Association System
provides step-by-step instructions on how you can add your file
If you look at the existing entries on shell.windows.com,
most of them have relatively straightforward and neutral descriptions.
"This document is a PowerPoint presentation."
"This document is a sound file."
But there is at least one company that decided to use the file association
service for a bit of grandstanding.
"Invented by XYZ company and perfected over 15 years,
ABC file format lets you capture information from any application,
on any computer, and share it with anyone around the world."
By the way, if the file association Web service offends you,
you can disable it.