With Windows XP the tcp/ip stack can be reset by following the instructions here.
If the problem occurs with Windows XP when trying to renew a dynamically assigned address and the error is "An operation was attempted on something that is not a socket" the repair is described here
With other OS versions there are free utilities to help repair the stack. Most of them are covered in section 3.0 of this FAQ.
If all else fails it is time to remove the drivers for the network card and reboot. Upon restarting Windows will start the "Found New Hardware" wizard. Reinstall the card with the latest drivers if possible. Then rebind TCP/IP to the card.
Feedback received on this FAQ entry: