most likely you can disable it in bios. ive never had onboard, but i assume that is where it would be located (BIOS).
-Epox EP-8KRA2+ with KT600 VIA chipset
-Athlon XP 2500+ Barton core
-160gb WD SATA
-Nvidia 6600GT agp
-1024 Mb Dual Channel DDR PC3200 corsair valueram
-Antec 430 Watt Truepower
-Windows XP Pro OS