EPoX unfortunatly went out of business 3 years ago (I have two of their excellent 9NPA+Ultra socket 9393 motherboards running in two systems). You could try doing a search for EPOX 8rda31 Ethernet driver
Be careful because there are a boat load of places that want to charge you. You could also try two very helpful cites: Rebels Haven which has the very latest BIOS updates, etc. for older motherboards. They certainly do for EPoX.
There is also the PC Perspective forums which still has people who will answer questions in the EPoX motherboard forum.