get Networking working

I have a computer that I put Redhat 6.2 on to mess around with linux. It has 100 mhz and 40 meg of Ram. I picked a custom install and choose to install everything. But I cannot seem to get the Networking to work. It has a 3Com Etherlink III 3C509 network card and if I use the command “ifup eth0” I get a message that said ther was a delay. How can I get this working. I choose the 3Com card in the Kernal tool and added it.