What is wrong with @IPADDRESS0 ? why don't you want to use it. They will always have one if they have a NIC or Dialup.

I found the IP Address in the following location on a 2000 system.

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\{503487BA-0B30-42A5-81AD-1E8EAF65F6B3}\Parameters\Tcpip