[idi banashapan]

are the HDMI and PC audio inputs tied? most tv's will only support one input at a time, where video and audio are coupled as a single input. the tv is probably expecting the audio over the HDMI cable if you are seeing an image (which means you have selected the HDMI on the channel select). The PC audio in and PC DVI are likely coupled, so you would only get the sound if you switch the input to PC, which will then look for the video over the DVI.

sounds to me like you're mixing the inputs and expecting both to give you an output simultaneously. this won't work in most cases.