Suspect that this may be something to do with the different way in which XP treats hardware ports. My terminology may be a bit imprecise but I think in XP you create "Virtual" ports and then XP assigns these to "real" ports.
Certainly, this is the case with Serial ports but with contemporary hardware XP is truly PnP and new devices are installed usually seamlessly.
But for a parallel port for the old 6L printer, well...
I'm full of admiration that you keep this printer going. My old 5L went to that big IT room in the sky long ago after I could no longer keep the paper feed under control.
So have a look at the Help/Troubleshooter for this and also, if you've not already done so, use the "Add New Hardware" wizard in Control Panel.