Updating the system BIOS is not done in WinXP, but at DOS level from a cold boot. My initial recommendation wasn't to update the BIOS, although this might help if the initial advice doesn't work.
The original advice was to update the SiS 730S chipset drivers. If the manufacturer of your motherboard has specific drivers for this chipset, go to their support website to download the drivers. To download the generic SiS 730S chipset drivers, go to SIS Chipset Driver Downloads
(enable cookies) and select Category: Chipset Utilities / Sub Category: IDE / Product: SiS 730S / OS System: Windows XP. You should download a file called ide203.zip and install it.
Chipset drivers normally install from within the operating system so you should have no problem installing it in WinXP. Just follow the instructions and let us know the results.