I and my brother both run Parallels Desktop 10 on iMac Retina 5K rigs. My VM with Windows 10 Technical Preview was balky at upgrading from the late 99xx build to build 10049, but it finally did it. My brother's will NOT upgrade past the 99xx build he now has, and he's getting messages that his version has expired so that he'll have to reboot every 2 hours to keep using it. He cannot perform an upgrade via Windows Update. It persistently shows "no updates available," even though that's clearly false. We can, however, download the ISO for Windows 10 build 10074. What I'm wanting to know is if it's possible to upgrade a Windows installation in a Parallels VM from a downloaded ISO, as opposed to making a new, separate Parallels VM for build 10074. On a physical installation, one would just boot the computer from optical media made by burning the ISO. On a Parallels virtual installation of Windows is something analogous possible? He has some critical apps that he'd really rather not reinstall -- MS Office which would almost surely involve the hassle of a telephone reactivation and an Adobe program called Authorware that would also require a tedious reactivation.