I have an HTPC that serves as my light desktop as well. I just got an HDTV so I am finally going to put this to use as an HTPC. But I still want to use it to do light computer duties. Where I'm running into problems is how do I easily control the htpc. I have dual monitor ATI card. Best I can figure is I have to extend the monitor. Is that the best I can do? Do I really have to drag mediacenter over to the tv everyday? This may sound dumb but I think I get most everything else except this. And can't find any answers out there. Id love to find a way for it to be there when I switch inputs on my remote. Or a hot button or something. Help!
This may not be the solution you are looking for, but the monitors could be set up as a mirrored desktop, rather than extended. That way, whatever is shown on one monitor is shown on the other. I seem to recall finding a setting somewhere on my ATI card that let me hit maximize on a window on one screen and have it maximize automatically to a certain monitor, but I don't remember exactly how I got to it. Good luck!
The other alternative is removing the desktop monitor entirely, and using the HDTV as the only monitor for your computing tasks. If you want to run that machine without turning your TV on, you can remote desktop from a laptop and work that way. This is how I have my HTPC set up. The only drawback is that this does not work for gaming.