Hi!
Well, that is an interesting problem then.
I looked around on the HP web site and couldn't find a manual for your
printer. The closest printer I have here on site is the predecessor to
the 2400, the LaserJet 2300DTN. I took a look at its onboard control
panel menus and found
Configure Device > I/O > Parallel Input > Adv. Functions > Off/On
I have my doubts that this will disable the port, as it sounds like
more of a setting for turning off bidirectionality of the port or
something. But it's worth a shot if you haven't already tried it.
What about the port on the printer? Is it covered by a door or cover?
I've seen some printers shipped with plastic protectors over their 36
pin Centronics parallel ports. If you could find one of those, you
could glue it to the port in some way.
As a last result, perhaps you could move the printer to where no
parallel cable will reach it. I would think that would stop all but the
most determined person. The longest parallel cable I've ever seen was
25 feet long.
That's probably the case.
William