Francis Hogle, the development manager for the Windows Media Center core team, has posted a really nice introductory overview about how Windows Media Center works behind the scenes. It uses diagrams and pictures to explain how we have separated the User Experience Framework from the Rendering Engine and talks about how these pieces talk to each other. If you've ever been curious about how Media Center was designed and built behind the scenes and how Media Center Extenders work, I highly encourage you to check this link out.
Also, the title of that post includes the phrase "Part One of Four" so I'm already looking forward to the rest of Francis' posts. Since his office is just across the hall from me, I'll have to stop by and bug him about this 🙂