Help with NIC!!!!!

I've just received a new computer with an On-board nic. It appears to be faulty. I would like to disable it, and install a pci network card, just to see if it will solve my problem. I'm a novice computer user, and I've never done anything like this before. What type of card should I purchase? I'm running an Athlon XP 2400. I'd rather do this, then send my computer in for service to swap the motherboard out. Help! Will this work? I have an onboard realtek 8139 right now.

there should be an "onboard devices" section somewhere in your bios. Or atleast something similar where you can disable your nic. As far as suggestions, d-link and linksys have both been reliable from my own experiance...