Could my network card be defective?

Here is my situation:
-2 comps with WinXP Pro
-Fresh install on both
-Comp1 has Cnet Pro200 nic pci card
-Comp2 has onboard Realtec ethernet
-Dlink switch

The problem:
Computers will not see on another on a network. The lights on the switch indicate both are connected properly. Removing the plug from either computer brings up the windows indication that a network wire has been unplugged.

Details:
First off, I believe that the problem may be that the Cnet nic in Comp1 is possibly defective (it cost $4 from some online store). I had problems networking Comp1 in the past, but I attributed it to differences in the OS. I am going to get another nic tomorrow to see if hardware is the problem.

But... I set up the computers with fresh installs of WinXP Pro about 2 weeks ago. Immediately after installing the OS, I set up the network using the Networking wizard, and they networked fine. Today, I came back over to my dad's and they weren't working. So I did a fresh install of WinXP on both and again tried to set up the network using the wizard. No dice this time. The computers will not see one another.

Does this sound like a hardware problem? If not, could someone please give me some suggestions as to a possible software solution.

Just an update. My theory was correct. The Cnet nic was defective. I replaced with a new Netgear nic and now networking is just fine. I just wish I hadn't wasted last night reinstalling XP on two computers