I have installed a new video card from Nvidia, and now there is no sound. When I check Sounds and Audio Dev, it says "No Audio Device". How do I restore the sound?
Does your OS see the sound card? You'd need to look in Device Manager to see if the OS even detects the hardware. If it doesn't, I'd try to reinstall the sound device's driver.
On a side note, I recently got a new GTS250 to replace an old dead ATi card and my onboard sound suddenly stopped working at the same time. The pair of USB speakers I have attached worked perfectly, but the onboard sound quit. I assumed the onboard audio on my old motherboard had gone flaky and simply popped in an old PCI Sound Blaster card which worked perfectly, but maybe there's something going on here. My computer did detect the onboard sound hardware and it appeared in the mixer as a valid sound device, but it simply refused to work.