What about uninstalling and reinstalling the drivers? Maybe even try an older version of them
I have a compaq laptop from 2001, and the newest drivers for win2k are flaky, when I boot windows I have about a one in five chance that they will "initialize" the sound correctly. If they don't, I get no errors, but if i play sound the eq in winamp shows that it's playing, but I hear nothing. But if I reboot and it initializes correctly, it stays working. My workaround solution has been to shut to to hibernate mode instead of powering off. FYI, older versions of the drivers always init, but the sound plays back about 10% too fast. So it certainly could be a driver issue