Click Start, then select Run.
Type "command" and press enter.
Type the following commands, pressing Enter after each command:
netsh int ip reset reset.txt
netsh winsock reset
netsh firewall reset
Note: Windows XP must have Service Pack 2 (or later) installed in order for these three commands to work properly. Otherwise, only the first command will work.
Restart the computer.
If the commands are typed in properly but errors occur, Windows networking may be heavily damaged. In addition, if these commands do not return errors, yet do not fix the Internet connection after the computer has been restarted, consider further troubleshooting: