Without knowing the motherboard model it is difficult to guide you to the exact link to the driver download. You may try this link and see it can find the appropriate drivers for your board: http://support.intel.com/support/motherboards/desktop/detect.htm
Please note this will work only if you are using intel motherboard and not OEM boards.
Also you may try to follow the troubleshooting steps in the following link. It is very well documented and may help you to solve the audio driver issue you are having: http://support.intel.com/support/motherboards/desktop/sb/CS-020642.htm
Advice: You may have to disconnect any front panel audio if there are any connected, during troubleshooting and update the BIOS if necessary.