How to troubleshoot wireless network connections in Windows XP Service Pack 2:
You may receive a "Limited or no connectivity" message on a computer that is
connected to the Internet by a DSL modem or a cable modem after you install
Windows XP Service Pack 2
Troubleshooting network connection problems
Go through the configuration again and make sure you typed the EncryptionKey
or Renter the Key in.
Open a run command and type in:
netsh winsock reset click [OK] and Reboot your machine.