So what other drivers have you tried? Did this one not work? Realtek 8139 driver
These specs say that is your network card, but also list a RaLink RT73 Wireless card dongle as maybe coming with it. Is that on your system and have your tried drivers for it? (Also note on the specs page that there is a switch that has to be on for the dongle to work.) If you can't get drivers for what you have on board, you may be up against buying a network card dongle like the RaLink.
Sorry about the confusion on the link. I can get to the page in the link, but when I try to perform the actual download I get a page not found, too. So you are correct that Advent is probably not supporting this product anymore.