It is taking the whole BaseUrl and adding it to the beginning of the MANUFACTURER URI. Anyway, If you are saying that this is a problem of the Windows Explorer, I believe you. I just needed to know whether there was a way to influence this.
www.foo.bar is not a URL. My guess is this "explorer" (no idea what this is) will detect that your device has a manufacturer URL that actually looks like a path, and then append it to the base URL to create an absolute URL.