Yes, you are probably right, after getting a bit more on the history, the explanation is probably that the printer suppliers set up the IP addresses, the computer shop did not dare to change them, or did not know they could. They then didn't understand why they could not access them from the 192.168 address which the router was handing out to the computer. They then started to try all kinds of things to make the installation work somehow, and came on the remedy of installing multiple network cards. And it did work, its just that when you come to change out the computer its a weird configuration.

Windows and the wizards are at fault, they give you the impression that you know what you are doing, but they're an obstacle to any real understanding outside that narrow world.

Not that I'm any kind of expert on any of this. Partially sighted would be a fair description! Anyway, we'll swap it all out when the new stuff arrives next week so we'll see.

Thanks a lot for the helpful comments. Its interesting to know that its not an unfamiliar sight, this sort of stuff.

Al