I'm assuming that you are running the GNOME desktop environment. If not, do me a favor and switch to it temporarily.
Before trying to configure your ethernet card, go to Applications, Accessories, Terminal. Type
and see if your card is listed in the output. If so, then close the terminal and follow this tutorial.
Go to System, Administration, Network. Type in the root password and then click OK. The Network Configuration window will popup. Under Devices, see if your card is listed there. It'll say something like eth0 for the nickname and Ethernet for the type. If the status is inactive, check the box next to it and activate it. If nothing is listed, then go to the Hardware tab. If your card is not listed there, then click on New. Choose type Ethernet and press OK. Choose your ethernet card in the topmost drop down list, and then click OK.. You will have to manually configure your DNS in the DNS tab. If your card is not listed in the drop down list, then chances are you will have to do a Google search for your card, and make sure that you download the Linux driver. The Windows driver will most likely not work on Linux.
I hope this helps. I don't use my ethernet card since I'm using a wireless card. If you have any other trouble, just respond to this post and I or somebody else will try to help you further.