Microsoft's WMV HD Content Showcase
Microsoft has a bunch of 720p and 1080p movies on their WMV HD Content Showcase website which demonstrates their WMV HD standard that uses the Windows Media Video 9 codec. While the quality is probably not as good as the best HD movie trailers offer by Apple, they are still quite good.
You will need the latest version of Windows Media Player to view these movies but if you have the codecs installed through other means (such as Codec Packs), you can watch in other players without any problems.
We'll provide some screenshots of the 1080p content available from the Microsoft website. Keep in mind they are compressed, so the quality is not going to be as good as the actual trailers but they'll give you a good idea of what is available. Click on the images below for the full 1080p screenshot.
Let's get started!