When you boot with the CD, try typing in
bf24
to boot with the 2.4 kernel.
and go through there. It may detect your network card automatically. If it doesn't, reference this page
http://www.scyld.com/network/rtl8139.html
and see if it has any additional information.
If I remember correctly, those should be automatically detected, and if not, you can go through the ones that are listed under the NET section, and try to activate the ones that look like they might work. Not a perfect answer, but something to work with...