A re-install of Windows and starting fresh will help, as you shouldn't get registry and driver errors as you will have to install them again and the system is back to it's baseline parameters. If you do this it will help with further troubleshooting if it proves necessary.
Another thing to do in the beginning would be to remove the PCI sound card as having 2 audio devices installed can cause shutdown issues and other conflicts within the OS.
You can download the drivers you need for Windows XP 32 from here:
http://www.gigabyte.com.tw/Support/Motherboard/Driver_Model.aspx?ProductID=3291&ost=xp#anchor_osFor your audio you need the first one -
Realtek Function driverThere is only one option for your Chipset
For your LAN you only need the first option -
Realtek PCIe LAN driverand you say that you already have the latest 10.3 ATI driver for your GPU