There is probably a lower level problem here. If the PC does not at least attempt to enumerate the USB device when you plug it it, its not going to be visible at any other layer.
So the first question is do you get the usual "USB device mounted" sound on plugging it in?
If not you either have a device that is not responding correctly, or for some reason windows has got itself confused during an earlier attempt to communicate with this device an has marked it out for different treatment thereafter.