I foolishly thought I had version 5.1.2.2 of XTU on the 8.1 (Although I did try downloading random versions on win7). Turns out I had one of the v4s when I checked Programs Installed. I uninstalled XTU (4.1 or 4.3) on 8.1 and tried to install 5.1.2.2 and waddayaknow, unsupported platform. So now...