Never use Windows Update for hardware drivers. It's a hit and miss affair and can install the wrong drivers.
Uninstall all your audio drivers completely. You may have to manually do so. Do not leave any behind.
Remove your PCI soundcard, then go to PcChips' website and download the latest compatible motherboard/chipset drivers and install them.
Install the sound card, preferably to a different PCI slot. (Depending on which card you are using. If it's onboard, obviously ignore this step) (I'd try onboard first)
Check it's enabled in the Bios and onboard is disabled (only if it's a PCI card), then go to desktop and install the sound card drivers. (See if C-Media have any updated drivers for your model onboard)