Thanks for your help on this. I didn't know the technical details of the usb port but I was concerned whether applying the power supply to the data lines would have caused damage.
I am puzzled that Windows says "usb status is not available on this printer". This seems to imply that windows knows there is a printer connected. I would have thought that failure would have been all or nothing. I would have expected Windows to say it could not detect a printer, not that it could not read from it.
After the incident I tried plugging the printer into different usb sockets on the pc (with the printer end the right way round!) but I still got the same message. However other usb devices, such as my mouse, still work, so the ports have not/had not been completely destroyed at that time.
I suppose the next step is to try to connect the printer to my laptop and see if it will work with another computer.
However, things have gone from back to worse. Last night I was idly surfing the internet when my screen went black and I heard the fans spinning down.
I haven not been able to turn the pc on since. I have not added or removed any hardware, nor installed any software. the only thing that has happened is this printer misconnection. Would that have destroyed my motherboard? If so, why the delayed reaction? Why did the computer continue working normally for some hours afterwards? Is this just an unfortunate coincidence?
I have disconnected everything so that there is only the graphics card plugged in. No mouse, no keyboard, all discs disconnected from data and power, yet the board will not come to life.
I don't have a spare motherboard to move things across to try but I may have a spare psu to see whether it is the psu or mobo at fault.
Any ideas what to do next? Or shall I buy a new printer and new motherboard ;)
TIA