I just installed a new video card and its drivers. The sound on my computer has now gone away? How can I get the sound back?

I have a HP Media Center PC. The fan on the video card burned out so I replaced the card with a GeForce 8400GS. When I put the card in, but hadn’t yet installed the new driver, the sound still worked. After I loaded the new driver sound on my computer no longer works. Is the driver on the Video card affecting the Audio?
How do I fix?