MediaPortal turns your PC in a very advanced Multi-Media Center / HTPC.
It allows you to listen to your favorite music & radio, watch your video's and DVD's, view, schedule and record live TV and much more. You get Media Portal for free/nothing/nada/nopes and best of all it is opensource. This means anyone can help developing Media Portal or tweak it for their own needs! Please read the requirements before installing MediaPortal!

Screenshots: Media Portal

Source: sourceforge

I have been thinking about a MythTV install, but unfortunately I have an old crappy MSI TV@nywhere card and it is not supported... but it is supported in windows and this media portal sounds right up my alley.