No sound, didn't have this before installing graphics card.?

I just got my new ati radeon graphics card. I have it installed and running good. But I went into itunes and doubled clicked a song, no sound. I tried multiple programs and games and got no sound. So I checked all my wires and settings and everything. I went into control pannel and it says that there is an HD audio device hooked up. All I've got are some external logitech speakers. I could find no option for changing the audio output device, and I even tried reinstalling my drivers. Can someone help me get sound?