|Installing a video card in a mboard slot should have no effect on your onboard sound.|
Make sure the speakers are plugged into the right ports.The speakers must be powered on.
See Response 6 in this
" Make sure you don't have volumes set too low or muted, for things you want to hear or use.... "
Note that the sound is Muted if the blue speaker icon below the volume slider has a red circle icon with a diagonal bar
Also see Response 5 starting at....
"A frequent answer of mine regarding sound software problems ....."
"When I looked at my specs, I saw that I had a video card (Intel GMA 950) and sound card that were integrated to the mobo. "
Intel GMA 950 is the onboard video - when a video adapter is built into the mboard IT'S NOT A CARD !
If the video CARD was installed in a PCI-E x16 slot, the bios automatically disables the onboard video adapter.
The onboard sound chip is built into the mboard - it is a separate chip from the probably two main chipset chips, one of which has the onboard video built into it. It may use the same IRQ as the onboard video, but that does not cause a problem. Any onboard devices that were designed to use the same IRQ does not cause a problem.