Sensible,
I checked the Advent Website and they did not have any information on the 8725. You could look for a chip on the motherboard that will say either VIA or AMD or SiS on it. The name and the model number on the chip would help.
You can also look in your Device Manager and expand System Devices. In there you will see Recourses that should be specific to the Chipset Maker for your motherboard. The other option would be to contact the company that made the computer and ask them which motherboard chipset your computer has. Then we could locate the correct drivers for you.
Since you have a Voodoo3 3000 Video Card, you will have a little trouble with 3D applications and games. 3Dfx folded before the release of WinXP so there are no official drivers released for WinXP. People have worked on their own to get some drivers to work with WinXP though. The latest I can find are:
Voodoolizer 1.04.01 BETA 6 for WinXP/2K
For your Sound Blaster PCI 128 here is a link to the WinXP Drivers:
Sound Blaster PCI 128 (Model CT 5808)
Take Care,
Richard