I'm not trying to take sales away from Parallels, but those Parallels 10 users who think they have to upgrade to install MacOS after Yosemite, it ain't so! If you already have a VM of Yosemite or earlier, or the installation disks to create one, these are your options: Upgrade the OS from within your VM providing you have the installation image download for a later OS Or If you want to keep an existing VM, duplicate it and rename it to something suitable. In the Parallels Desktop window 'Add existing virtual machine' and add the duplicated VM When it raises a concern about it pointing to an existing MAC address, click the 'Create new address' option In Configure, rename the VM again as Parallels may ignore the filename you've already given it Launch the VM and install the OS of your choice Note. This will take you as far as Sierra. Unfortunately I tried it with High Sierra and though I could download the installer from the App Store, the installation itself failed. So if you want a High Sierra VM you will need a more current version of Parallels.
