HP LaserJet 3100 All-in-One Printer series - Manual (Page 267)

266 C Changing Parallel Port Modes EN
Other areas of potential conflict
In addition to the parallel port mode being set incorrectly, there may
be other areas of potential parallel port conflict involving software and
hardware from other manufacturers.The HP LaserJet 3100 product
cannot share the parallel port with other peripherals. If none of the
options in the Setup allow the HP LaserJet 3100 product to talk to the
computer or you have other devices that need a parallel port, you can
add an external ECP parallel port card to your computer. Then,
connect the HP LaserJet 3100 product to one of the parallel ports and
connect the other devices you have to the other parallel port. These
parallel port cards are available at computer stores and will allow your
HP LaserJet 3100 product to communicate with your computer
without conflicting with other devices.