This may or may not help. I have the same board as you two with a 700 Duron OC to 900. I have a 30GB MAxtor 7200 RPM ATA100 drive and a 450 MEG Seagate PIO2 drive on the same line. A TNT2 M64 AGP card. Using the on board sound I recieve no problems. I use the latest, NON-BETA 4 in 1 drivers and the ORIGINAL AC97 sound drivers that came with my CD-Rom. (not the latest one from the VIA hardware site.)
hope that helps a bit
Fighting a one-man-war against Windows.