MythTV on Windows (new)
MythTV runs and is officially supported on Windows but an official exe is not distributed, here is how to build a windows binary for yourself.
Using MinGW as the build platform, and MS Direct3D as the display layer.
Unofficial Windows Pre-Builds
A MythTV user has set up a website where you can download pre-built versions of the windows port, some of the information on that site may be incorrect, but the downloads may help some.
Note that these builds do not run on Windows 2000 (which lacks the 'freeaddrinfo' function -- see http://msdn.microsoft.com/en-us/library/ms737931%28VS.85%29.aspx).
The site is located at http://members.iinet.net.au/~davco/ and has versions 0.21 through 0.26 available. The page also has links to many more archived downloads.
Fixes builds are available from another user at http://mythtvwindows.sourceforge.net/ Experimental 64 bit builds will be uploaded when they succeed.
The frontend, backend (without most tuners), and most utilities compile, and most functionality works.
What doesn't work?
There is currently no support for most tuners in mythbackend. However the network connected HD Homerun ATSC, Cable or DVB-T tuner does work, as do a "virtual" tuner using a mpg file in a loop.
Win32 Build Script
The current Windows build script is https://github.com/MythTV/packaging/Win32/mythbuild.sh with instructions at the top of the file.