All that was needed was to make sure the Gateway address settings on the Desktop NIC, Printer's TCP/IP port address were identical.
On the HPLJ4:
In the Menu Configuration Setting AUX IO
BOOTP = NO
GW 192.168.2.12 <-------
WinXP - Networking
Configure TCP/IP on the desktop NIC with
GW 192.168.2.12 <--------
The PC will detect the connection between the printer and the desktop's NIC when the printer is turned on.
WinXP - Printers
Add HPLJ4 printer
Create a TCP/IP printer port with an
IP of 192.168.2.12 <--------
Select a generic NIC card.