I'm trying to set up an ethernet home network with two computers and they each have an RJ-45 port on the motherboard. One is a DFI LP UT nF3 250GB and the other motherboard I don't know but it is an emachines. My question is, do I need to buy an NIC card for einther of these computers or do I plug the CAT-5 cable into the RJ-45 ports on the motherboards?