Onboard Audio Not Detected In XP

Hi, like the topic name states, my onboard HD audio, the ALC888, is not working. I'm using a MSI G31 mobo with XP Home. Every now and then, the output will be disabled, and it's really annoying! When I go to Sounds and Audio Devices in Control Panel, it says No Audio Device, and everything under it is grayed out. I reinstalled drivers several times already, both from Realtek and from MSI, with no luck. The device shows up on Device Manager without a problem, though. Help would be really, really appreciated! Thanks in advance!