Are you trying to connect using a cable? The network card is what you use to plug the cable into the back of the computer. Are you connecting using WiFi? There is probably an antenna at the back of your computer; the network card is what the antenna is attached to.
If you open your PC, you'll see the network card is literally a card that plugs into slots on your motherboard. The make and model of the card is usually found there.
I had suggested this earlier -- if you go to Start, right-click on Computer, Manage>Device Manager, is there a yellow or red icon over the Network Adapter icon? Did you try this?