Nick,
Something must be messed up if Windows can't find the driver for the Ethernet card. Windows comes with drivers for most common hardware, and I would think a run-of-the-mill ethernet card would fit that category. Otherwise, find out who made the ethernet card, go to that company's website, and download the drivers (they should fit on a floppy, or USB memory stick thingy) Does your PC even have an ethernet card? How do you connect to the internet? You're not on dial-up are you? More details please!