Thank you for your welcome suggestions, unfortunately they did not work. This was because, after a bit more fiddling I decided to try another device to the USB port and found that it didn't work either. The port is one of 4 on a PCI card. Plugging my 2 non-recognised devices into my Mainboard USB ports gave instant recognition. Problem solved.
Again, Thank you for your prompt and informative reply.
Bill Gadd