UPnP with Windows Media Player
Windows Media Player 11 includes a UPnP server and client, allowing it to share media with other UPnP devices, and to view media from other UPnP devices. Fortunately, that means it's capable of accessing music and recordings from a Mythbackend.
Whilst Windows Media Player 11 (WMP11) is capable of accessing a MythTV Backend, it does not include either the required codec support to view recordings nor the required container support to open MPEG Transport Stream files. That said, the MythTV machine should be immediately visible in Windows Media Player's "Library" view, as soon as sharing support is enabled - it will simply throw an error if you attempt to open an unsupported file.
At the moment, this is only available under WMP11 in Vista. First, share viewing support must be enabled in WMP11. Click the little arrow under Library, then Media Sharing. Tick the box marked "Find media that others are sharing" then OK. This should enable viewing support.
Next, you need to enable support for the MPEG Transport Stream container used by DVB recordings (and possibly MPEG Encoder Cards like the PVR-150 too, but this is untested). For this, we will install the Haali Media Splitter - this primarily adds support for the Matroska container format, but as a secondary effect, adds support for other formats including MPEG-TS. It can be downloaded from The Haali website.
Finally, you need to enable support for the codecs used in recordings - typically MPEG2 for video and MP2 or AC3 for audio. If you have a commercial DVD player such as PowerDVD installed this should already be supported - otherwise we will use FFDShow. FFDShow is based on FFMPEG, which powers all of MythTV's media support, but plugs into the Windows DirectShow codec architecture. Download the latest build from the ffdshow tryouts website, and install it. During installation, be sure to enable support for MPEG2, which is disabled by default.
All of the above should enable you to both view your MythTV backend in WMP11, and to double-click on a recording to view it.