|Try re-installing the driver. You can find out what sound card you have by going to the device manager.|
to access the device manager right-click "my computer" and choose "properties" click the "Hardware" tab then click the "Device Manager" button.
A window will open that has a list of all the hardware in the system, Look for the sound card and then go online and search for the correct driver.
if you have a creative sound card you can go to the creative website to obtain the driver