I just got a Like-New Plantronics Gamecom 780 headset off Amazon. I installed the Dolby program from the disc, plugged it in, set it as my default speaker, but I still can't get any sound to play. The sound doesn't play from my original speakers, and it doesn't play from my headset either. Can someone tell me what the problem is? The volume control and the Dolby 7.1 surround sound switch work fine, so I doubt it's broken.