Unplug scanner, plug into different USB socket (not monitor)
Try scanner on another PC (does it work there? scanner probably not broken)
Bring working scanner to original PC where non-working one was (with the working USB Cable)
Working scanner still working
Try it here with the cable from the non-working scanner
Working? re-plug in non-working scanner back call CDP
Not working? could be a bad USB cable
Working scanner does not work here - possible issue with the USB port, try another usb port.
If unknown device is present no matter which PC the scanner is connected to - then it may need repair.