I do this with Windows 7's included Media Center as a PVR. I was surprised when checking out popular "media center" software that most of it seems to concentrate on playback of videos and not support being a PVR.
I did that as well, I had two tuners plus an external HDTV adapter with an IR blaster. I would make my own cable channel line-up pretending I had cable and satellite. The nicest aspect was that the xbox360 on the other TV could also stream the content from the media PC and it did not require a gold subscription.
