Read up on the HD Homerun in this thread:
http://thegreenbutton.com/forums/thread/160595.aspx
A few things you want to keep in mind while reading that thread are the following. While this may be over-simplified, I think you'll get the point:
First and foremost, do not get intimidated by the birrage of information you're about to read. Quite the contrary, you're about to enter the realm of 'early adopters' so the fact that you're taking this step should be very encouraging.
Now, when you read the other thread, you'll see references to QAM all over the place. Again, in the interest of simplifying this, QAM refers to a digital signal that the cable companies deliver over their wire. For the most part, that signal includes the local high definition stations completely unscrambled. If you were to just plug this wire into a QAM capable TV, you woud get your local HD stations without the need for the cable company's decoder box, also known as a Set Top Box (STB).
So, the HD stations are contained in the QAM signal on your cable wire. You want to get those stations displayed on your shiny new HDTV. Vista and Media Center do not support QAM tuning natively. That is to say that there is no way for your Vista or MCE PC to display these local, unscrambled HDTV QAM signals. This is where HD HomeRun comes in. This is a small device that needs to be connected in 2 different places in order to work properly: 1 - Your cable wire. 2 - A network which is also connected to your Vista PC (You can also connect the HD HomeRun directly to your PC's network port, but we're going to assume you have a home network to 'hang' this device off of.)
Still with me? Good. I'm not going to get into the particulars about how to set up the HD Homerun here as I don't even own one yet, but the basic theory makes sense to me. The HD Homerun receives the QAM signal off the cable wire, and is able to 'decode' the unscrambled stations, and then it's ready to deliver this signal to your Vista PC, over the network connection, in a format Vista is able to understand and display.
On your Vista PC, you need to do some leg work. Follow the HD HomeRun instructions for setting up Vista's program guide. Vista does not know about these new HDTV channels it's about to start getting. You're going to have to tell it what channels they are and how to tune them in. I know, that sounds like (shudder) programming but it really isn't, so you can relax. The documentation for HD Homerun looks pretty good, so you should not have any problems going through this step.
Now, just tune in those sweet, crisp, clear HDTV channels. Please keep in mind, though, that you are only going to get unscrambled QAM (Clear QAM) channels. These will include your networks, maybe a few others, but do not expect anything that the cable company would charge money for. Channles like ESPN HD, TNT HD, Discovery HD, InHD, and of course, HBO HD are almost always scrambled.
With the current state of this particular endevor, I would recommend this solution. It'll cost you soewhere in the neighborhood of $120 or something like that and it's the most reliable with the least cash outlay. The Firewire solution is very high maintenence, frustrating and flakey. Although i'm using it as my solution, I would not recommend it to a self proclaimed Noob. The over the air solution is nice, if you're in a major metro area and can pull the stations in. I'm just outside of Raleigh NC, and due to the hills around me, I can only get Fox to come in reliably.
OK, so you're ready to go now. Click on that link up there and go read up on this solution. First, you might want to pour yourself a glass of wine, as it's a very very long thread already! Again, do not get intimidated. Anyone can do this stuff with a little patience, some research and a lot of help!
Ghostlobster
Very happy convert to SageTV! Finally, watching ESPN-HD in real HD on my HTPC without having to deal with the CableCARD fiasco!