When you use the Ipconfig.exe tool, the wrong DNS server may be returned.
Windows XP Ipconfig.exe is NOT aware of DNS configurations that are applied by Group Policy and
returns the DNS IP address from
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\<YourNetworkInterface>.
When Group Policy assigns the DNS IP address, it is stored at
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows NT\DNSClient.
To workaround this issue, you could use the
Netsh command to dump the information.