I've see this problem posted a few places but not a good solution (maybe there isnt' one). Here is my set up.
HP a1640n running windows 7 home premium
PNY Nvidia GT 240 with HDMI output
Panasonic TH-42PZ700U Plasma TV
Yamaha HTR-5830 receiver with Polk RM7 5.1 speakers.
I've connected my video card to the TV with the HDMI cable and there is an optical cable running from the TV to the receiver. Apparently the TV will only pass through 2 channel audio via the optical cable (although when I run hdmi from my old dvd player to the tv, then use the same optical output to the receiver it tells me it is dobly digital or dts and sound very good). I have not found anyway to to have windows send more than 2 channels through the hdmi to the TV. So here are the two solutions I am considering but having issues with.
1. Use the current onboard sound card in my computer and send the audio directly to the receiver via the coaxial s/pdif. The problem is the gt 240 being installed has disabled the onboard sound and I can't get windows to find it again even if I disable the hdmi audio under device manager.
2. Get a new sound card with with either optical or coaxial s/pdif output and run that directly to the receiver. I imagine that plugging in a pci sound card will allow me to then choose between the gt 240 sound and the new sound card.
A few other questions...
1. Does it matter if I get a 7.1 or 5.1 sound card since my receiver is only a 5.1 receiver and I only have a 5.1 speaker setup?
2. Since I am doing all this to play blu ray movies on my PC should I just go buy a new receiver with HDMI input and DTS HD processing and forget about the other sound card issues?