Can you make sure you have a driver installed for your network card?. If you look under your Device Manager (just search Device Manager on your start bar) and verify that you have a network card listed under Network Adapters. If you do not, and have some Unknown Devices then you will most likely need to go find a new driver for your card.
That could be difficult if you don't have access to a machine with the Internet, but sometimes in a pinch, the Vista driver will work if you have the disk, at least enough to get you online to get the latest.
Hope this helps.. if not, please provide some more info, like what your IP configuration is, etc.