1. Click Start, and then click Run.
2. In the Open box, type netsh int ip reset resetlog.txt, and then click OK.
Note: If you are using Windows XP SP2, in the Open box, type netsh winsock reset all, and then click OK.
3. Restart the computer.
Note: When you run this command, it will rewrite the pertinent registry keys used by the Internet protocol (TCP/IP) stack. This achieves the same results as removing and reinstalling the protocol.
To fix this problem automatically, go to http://support.microsoft.com/kb/299357 and click the Microsoft Fix it link.