Hmm ... I'm guessing that the motherboard is a VIA chipset since just about all motherboards that support an AMD chip are. Even though I couldn't find your motherboard in the product listing on Soyo's home page, I'm 99.9% sure the motherboard has a VIA chipset in it.
That being the case, the problem could be any number of things. Unfortunately it all really stems from the VIA chipset though. If you can, try replacing the video card with a PCI video card. For some reason I've seen that fix a lot of problems with VIA motherboards. Also, if you can try putting different memory in.
If you can't then best of luck. Welcome to the world of VIA.
Either way, if you can in any way update the motherboard's drivers, there may yet be hope. I'd severely hope that somewhere on the Soyo page there are drivers. If not, there should be on VIA's page. I don't know if VIA's 4-in-1 drivers would work for your motherboard or not.
Anyway, if you can't guess, I'm almost sure the problem is related to your motherboard. Especially it being an older AMD chip meaning it's probably on an older motherboard and thus using an older VIA chipset.
Best of luck.
- Sanity is purely based on point-of-view.