Hey there, it would help out if I could understand a bit better what you are trying to do. Did you want to use your PC as a home theature watching HDTV/movies or did you want to use your HDTV as your computer monitor?
I use an ATI HDTV Wonder card so I can help ya out if you need to go that route.
Also the AVS forums
http://www.avsforum.com has a wealth of information.