If you have IMS Ver 2.4.x.x the USB is not a selectable option until later IMS for LON. You can use a serial lon talk adapter (SLTA). If you do end up with a SLTA and only have one serial port, use your serial port for SLTA . Get a PCMCIA to serial for your second serial port. All Drivers are available on Echelon website. I believe IMS Ver 2.5 and above will allow you to select the U10 USB Lon Talk Adapter. I see the U10's on ebay for about $200. The SLTA are hard to find like PCC-10 Card.