This may not be the answer you want to hear, but have you tried compiling your own kernel? Perhaps the kernel provided by knoppix may be a little overkill especially if you're loading modules you don't need. If you're too new to do it, you can go to www.kernelnewbies.org and read up on how to roll your own. I think everyone should at least try once because no two systems are the same and you can trim the fat from the kernel and/or add features that you desire. It's a hair-pulling experience when trying to come up with the best configuration but in general, it's worth it. OTOH, Klaus had every module for sound including alsa compiled with the kernel, have you tried alsa? It's said to be more robust than oss, and should enable you to use the external mute button, but then again, you can also mute it by using kmixer if you're using kde as your desktop environment.