Problem with TV card?

I have installed a Mecury TV capture card on my PC. For me to watch any TV program using the TV card I have to plug in the speakers on the TV card and then replug it on the PC's sound card to play movies or music on the hard disk. The problem I have is when I try to capture TV programs or from any external source using the TV capture card. The capture of video is okay but there is no audio in the capture. What could be the problem?

Problem with TV card?
It could be that the computer's using the wrong sound input for it's source. Click on the speaker (sound settings) on the task bar. When you get to volume control, click on "options" On the window that comes up, you'll see a tab for "mixing" device, or input device. Click open the dropdown menu, and see if you're T.V. card's sound function is listed. Should be all that's needed.