If you use
WinXP remove the sound card from device manager and restart the computer, is going to find it and
WinXp is going to install a generic driver for your hardware.If you use a different OS find the manufacturer site and download the driver for your card.If is a card problem you don’t have any sound on your pc if is a codec is just for an avi file.Download and install AC3 filter : http://www.free-codecs.com/download/AC3_Filter.htm