Glad you got everything going, who knew that Vista would come through to save the day?
FWIW, the USB to serial device I have is the one recommended by Mike Reagan in one of the Lionel videos (may be a Tripp-Lite?). Anyway it works perfectly with the Legacy programs and my Legacy system. Just gave up on it with the DCS loader. However, that was Win 7, I haven't yet tried either one with Win 10.