I tried this upgrade twice. When toolbox tries to install I get an error message telling me to reboot. When windows comes back it comes back low res and mouse disappears when you move it into the frame. Then you get an error message telling you that Windows cannot find your desktop and to run a network problem solver. That does nothing. Neither does following the recommendations of the Knowlege base article that support sends you. I used Time Machine to restore Parallels 15. but I also had to restore my Windows image file because whatever the upgrade did, it also queered my Windows installation. Second round produced the same results, so my recommendation to anyone considering this upgrade is forget it.