iTunes can supply the movies and TV shows, of course, but there's no way to watch them within Windows Media Center. (Actually, there's a plug-in----that makes this possible, but it doesn't support Windows 7.)

That leaves Amazon's Video on Demand service. Although it offers no direct integration with Windows Media Center, it does make watching your downloaded videos easier than you might think.

To get started, download the free utility to your media-center PC. Install it, run it, and then sign into your Amazon account.

If you've already purchased some videos, just click the My Videos tab in Unbox, choose the one you want, and download it. You can also shop for movies and TV shows within the program, or just use your Web browser.

By default, the program will save your downloads to an Amazon Unbox subfolder within your Videos folder. The next time you load Windows Media Center, navigate to Pictures + Videos, Video Library, then click the Amazon Unbox folder. Presto: you should see your downloads! Choose one and start watching it like you would any other video. (Note that you can't start watching a video until Unbox completes the download.)