Printing .prn files
As your printer is connected via USB rather than by the parallel port, and DOS can not recognize USB, the copy-to-printer command can not work. This is one downside of USB printers.
As you learned, you cannot put .prn files into Word or any other WP or text program. They are in a special format recognizable only by the designated printer and others of that type. A .prn file created for one type of printer may not print to a printer of a different type.
You will, therefore, need to connect your printer via the parallel port or else get third-party software to print your .prn files. One program that might work is Fastprint, which costs $40. You can download a free trial version (with some features disabled) from
I do not currently have a printer connected via USB, for the above reason, so I can not try it in that mode. It does work with my LPT connection but then so does copy finename LPT1.
If you do try Fastprint over USB, please let me know if it works.
Hope this helps