In a comment on a post about Longhorn, my buddy Michael writes:
I’m confused about one thing: [Paul Thurrott] has a lengthy discussion about Windows MCE 2005 and it’s support for HDTV. But he has it as “already been released”, but I thought it was still a few months away. (maybe he’s talking beta release?)
Windows Media Center 2005 is out now. I’m running the official release. A few sites have recently posted details about a rumored upgrade this fall; as far as I know, that upgrade isn’t in beta yet. According to the rumors, HDTV support via Cable Card will be a feature in this upgrade.
MCE 2005 does indeed support over-the-air (OTA) HDTV. I have a Fusion HDTV card in my Media Center test computer. I hooked up a simple indoor antenna and I was able to watch broadcasts from one local station in HDTV. Unfortunately, I couldn’t get a reliable signal from any other stations, making the indoor antenna experiment a bust. I’m off to Radio Shack for a new antenna one of these days to see if it works any better, but it looks like an outdoor antenna is the best way to get access to OTA HDTV.
The Fusion card is QAM-compatible. I’ve done a fair amount of reading on the subject and in theory, it should be able to decode an unencrypted HDTV signal from my cable company. I don’t think that MCE 2005 supports QAM, however, only ATSC, and thus it can only tune OTA HDTV channels for now. I’m still trying to wrap my arms around how all this technology interacts. If anyone has any insights to offer, feel free to add them in the comments.
Ed Bott 
Have you been able to get the fusion card running along with an analog tuner card. I have two AVerMedia 150 cards in my mce 2005 box and have not been able to get the fusion card to run with the analog tv cards. I have heard that MCE 2005 is suppose to support two analog and one digital tuner.
Yes, I was able to get it to work with a Hauppauge PVR-250MCE analog card. I had a lousy indoor antenna so it didn’t give me the channels I wanted, but it did set up and configure properly and I was able to view some HDTV.
The Fusion HDTV DVB-t Plus has a video-in plug. This does not work with MCE 2005 so forget having a cable/VHS/Satilite in conjunction with your HDTV. The card does not have a radio tuner and the manual is incomplete. Don’t install the remote drivers or you will bugger up the MCE remote (volume, play, rewind, fwd, pause dosent work). I had to reinstall MCE to fix this remote problem.