This the fix applied to printers that are having issues recognizing the port they are connected to. I experienced this issue on Windows XP, and may apply to other Windows OS. 

Run regedit. Go to
HKEY_LOCAL_MACHINE/System/CurrentControlSet/Control/Print/Monitors. Look for
a USB Monitor entry. Before doing anything else, backup the registry entry by
right clicking on "Monitors" and selecting "Export". Give it a name and
locaction so that you can put it back if you have problems later. If "USB
Monitor" is not there, add it by right-clicking on Monitors, New, Key. Name
the new key "USB Monitor". Once added, right click on the new key and select
New, String Value. Name the new value "Driver". In the right portion of
regedit, right click on the new "Driver" value and select "Modify". Make the
value data "usbmon.dll". If there is an "HPUMON" entry (or the like), delete
it. Disconnect the USB cable to the printer. Run the "scrubber" or clean
utility (Cleanspl) (do not remove USB Monitor - If asked to), reboot the
machine. Reconnect the printer and install the driver software per
manufacturer instuction. This fixed my problem. Good luck and remember to
back up your registery beforehand or create a restore point!

Link:

http://www.pcreview.co.uk/forums/cannot-install-usb-printer-specified-port-unknown-t3085597.html