Can you see your NIC in the device manager? If your trying to install drivers you should be able to.
With your reinstall, did you erase the contents of the old partitions and create new ones?
Do you use onboard lan, or do you have an extra card?
If you have erased the contents of the old partitions, and your starting from scratch,
Download drivers for your specific nic, or create a file with the install of the driver disc that came with your nic.
Within device manager, do not attempt to do an automatic install of your drivers as they probably won't be detected.
Manually install the drivers from within the device manager using the file you created.
You should then be able to connect to the internet.