I have been having another look at this and have become quite intrigued by the syntax of the "filename that will be used for printing" e.g. the one quoted in the VirtualRPC-SE Manual - which is HostFS::HP_Laserjet_4L
If you think about this you can see why you get an error message "Disc not found" when you give it an invalid name.
Also, I think the way that Microsoft and Acorn file systems interchange the use of the 'dot' and 'slash' characters may have something do with why we are not getting networked Windows printers to work when they have names like //computer/printer
Having said all that, I think that the way it seems to interface to the Windows printing system is quite clever and I now have it working to networked printers on a number of other computers.