Your Knoppix 3.1 version (released 2003/01/19) is too old to run properly on the young AMD64 motherboard and sound chipset. You mentioned that Windows XP runs fine but Windows XP released in 2001 is too old for the young motherboard & sound chipset. Either you installed the up to date sound driver from CD or the sound driver was downloaded & installed. You will need to download a more recent version of Knoppix, perferable Knoppix 3.8.2.