After corrupting a working installation of my RX Ensemble II, I finally got the drivers to successfully re install AND point to the right hardware i.e. LibUSB device by doing this with PC running, then plugging in RX Ensemble II via USB:
Sometimes you will need to remove ALL USB connections, including keyboard and mouse! Reconnect once the Softrock USB is detected. Dave's explanation of USB connection problems http://groups.yahoo.com/group/softrock40/message/56146
I had previously forced the LibUSB driver to install using Control Panel, add legacy device, Lib USB, etc.. Only problem was that using this method did not point driver to correct device/port. I know the CPU and its USB connection looks a HID, same as KB/mouse, to op system, still a little puzzled as to why this worked, but it did.
Thanks for the patient advice.