My WinXP installation didn't need drivers for the K7S5A's onboard sound, but Win2K did. Funny thing is I tried the CMedia drivers first from ECS' website and everything installed fine, but no sound would come out of the speakers! So I scrolled further down the drivers page and downloaded the SiS 7012 drivers instead and it worked fine. Both have the K7S5A listed as a supported mobo...
