The tlan was a pretty expensive card back then. Was the Deskpro model the same as yours in that particular post? What model is yours?
If the models are the same, go to a terminal as the root user and type:
modprobe tlan
Edit: If the tlan doesn't work you may have an intel EtherExpress Pro 100, so try typing
modprobe eepro100
and see if anything happens.
Then take a look and see if the ethernet lights come on. If not, the tlan isn't the right card, and we need to keep looking.
If the lights are on, then assuming you use DHCP on your router type:
dhcpcd eth0
This should assign your card the IP address and get all information needed from your dhcp server. At this point you should have net access.
If this works, we'll make it so that it is all done automatically on boot. If not, we need to keep looking to see what the chipset is on your mobo, or you'll need to find an extra PCI ethernet card sitting around.
Jim
Edit: Just thought of something. Do you get any output when you type
lspci
at the command prompt (might have to be root)?