While you attempt to create an LPR printer on Windows NT, one of the following error messages may appear:
Windows NT 3.5x
Could not add port: The printer already exists.
Windows NT 4.0
Specified Port cannot be added. The printer already exists.
Specified Port cannot be added. The port already exists.
The TCP/IP printer port address you are attempting to create was already created, possibly from a previously created and then deleted printer. The IP address remains in the registry to simplify adding future printers.
Check to see if the port exists before trying to add an LPR port.
In Windows NT 3.5x, existing LPR ports will be listed at the top of the "Print to:" list box in Print Manager.
In Windows NT 4.0, existing LPR ports will be listed at the top of the "Available Ports:" list in the Ports tab of the Printer Properties.
In Windows 2000, existing LPR ports will be listed at the bottom of the "Use the following port:" list in the Add Printer wizard.