USB mass storage devices just means its reading as a flash drive, which the gps may or may not do. I doubt the gps reads map files in this way.( some gps's do it this way, but because you said the website was trying to detect device, not just download a file to harddrive/storage device probly not yours) You need to get driver software froma cd or download from gps website for pc to recognize gps. When you got the wizard prompts, thats just windows attempt to install generic driver which would do nothing but hurt.