Having been bitten by the media center bug a few months back, I "retired" my old machine to a closet under the stairwell where I thought it would live out its life as a Tivo on steroids. Sure, I spent maybe $100 upgrading the video/sound, but that would pay for itself soon enough.
At first, everything was fine. I had originally reconciled myself to the fact that my old machine wouldn't support HDTV, which was fine, as I didn't yet have an HDTV display. Then one evening, my friend Pat showed me his new Sony setup, and I was hooked.
A month later, I've got a 56" Samsung 1080p DLP sitting in my living room. I knew that I would need a Comcast HD STB to play & record HD content. But what I didn't realize is that with my existing components, it's a three remote operation to switch between the HD STB and Media Center. A major pain...
Why not just use the STB for everything? Because the UI sucks (next to Media Center), and it has far less recording capacity than my old machine. What about a Harmony remote? I don't want to spend $200 just because none of my four existing remotes have the one nugget of programmability I need. Plus, I like the Media Center remote.
If only there was a way to run component video from the STB through the Media Center, or vice-versa. I'd have just one signal input to the TV, and things would be much simpler (but still not a one-remote setup.)
Meanwhile, I've read about the hack that lets you record HD on Media Center from the FireWire ports on some STBs: http://blogs.msdn.com/peterrosser/archive/2005/10/25/Firewire_Recording_on_MCE.aspx
As luck would have it, my old PC is just old enough that it can't support a video board with enough horsepower to play back an HD signal. So, I now have a monster Media Center box on order from Monarch Computer. At this point, I've blown well past $4K on this "upgrade", and my brain hurts from all the cable plumbing I've had to think about.