Quote Originally Posted by nugie
1. I cannot hear any sound from my speaker when I play mp3 with xmms( my soundcard is onboard AC 97 and it's already detected , volume Kmix is high , sound system enable , and I've checked all option in sound card configuration menu , the xmms play the mp3 like usualy with no error massages )
See this: http://www.knoppix.net/forum/viewtopic.php?t=17256
It could be that aRts is not releasing the sound driver so that xmms can use it.
You have already done most of these checks, but did you check xmms->options->preferences->audio->output plugin is set to use aRts? I'm not sure if your Knoppix version comes with the aRts plugin but if it does not, go to KDE Control Center->Sound & Multimedia->Sound system & set auto-suspend to 1 second.

Do you get sounds when you try to play the sample /usr/share/sounds/startup.ogg?