No sound with HDMI.

Hello,
I have looked at other forum posts explaining about going into the playback menu and disabling and enabling the HDMI driver, or going into device manager and doing the same thing there. Unfortunately neither of those methods work.
I have narrowed it down to 2 things that I think may be causing this. I recently bought a plantronics 995H wireless headset and have been using that. This pos already happens to interfere with my wifi (which is an entirely separate issue I have to figure out). So based on the fact that it interferes with my common netgear router, I wonder if this software messed up some setting on my computer.
The other thing that I think could be causing this, although I really hope it isn't, it could be my graphics card? I have been using an ATI HD5700 card for over a year in a HP computer with a barely adequate power supply. Could my card have gotten damaged somehow?

I could really use some input because I really like having my computer down in the theater room with the surround sound and giant HD projector. It is really frustrating that I can't get sound.

Thanks,
Nic