My computer has two printers connected to it. 1:a HP LaserJet 5L on lp1 connected to the port on the mother board. 2:A HP Office Pro connected to a PCI card in the system. I did not try to configure this. When I used printtool it detected only on printer identified as lp0. I configured it but no printing. Error Message said printer was not configured (the queue was written to however). The solution I find to configured the printer was: 1-REboot and disconnect the HP Office Pro. 2-REboot 3-Use printtool. Here it detectged lp0 (not lp1) but I the configure worked fine and I am able to print. 4 - I rebooted and reconnected the HP Office Pro(I use it in NT 4.0. 5 - REbooted Linux and Laser Jet still works fine. It seems that with an extra printer connected to a PCI card printtool is unable to configure the printer connected to the Port on the mother board. I did not try to configure the Office Jet Pro as HP says there are no drivers for it.
Did you originally (with both attached) have it set as lp0 or lp1 - unless you've explicitly loaded support for the PCI parallel port card, the printer would *still* be on lp0.