Use Device Manager. In the Start Menu type device into the search bar. In the Control Panel section choose Device Manager.
Find your audio device - probably in the Sound, Video and Game Controller category. Click on the small triangle to expand the section.
Right mouse click on the audio device and choose Update Driver Software. Use Search Automatically for an online search.
Not found? What audio device is installed? Realtek AC 97? Then look on the Realtek AC 97 website