No internet

I recently had my computer reformatted but when i was installing the drivers i didn't have a driver for the Ethernet cord. I don't have a lot of knowledge about computer only a little but my friends do and were all stumped with this problem. My computer at first would not recognize my Ethernet cord. i tried using the dell CD that came with my computer with the drivers and diagnostics but nothing in there helped me with the the Ethernet driver. i was told that a Ethernet card would work so i tried that in one of my pci slots. After i installed it, the card was not recognized so i tried this again in a different slot with the same luck. The guide to the card said that when it was first put it a bubble would say new hardware recognized. It didn't. After installing it again several times i still had no luck. So i am confused on why it isn't even recognizing my Ethernet cord and why none of the pci slots are recognizing the the new hardware. i need help immensely. Reply or email me at mcook13@kent.edu