|Sis650 drivers for 98 (but not 95) are on the Sis download site.|
Apparently the audio chipset on that is the ADI 1885 and I believe there are both soundmax and AC97 drivers for 98.
According to this:
that motherboard is an OEM Asus P4S333-M. You might check the Asus support page and see what they have in the way of 98 drivers.
Real men don't use AntiVirus; they just reformat