September 2019: On my seven-year-old Mac laptop, I use Mountain Lion, but about twice a week I need to do some work booted into High Sierra. I use Preferences -> Startup Disk to make the switch back and forth. I get regular emails advising me I can update my Parallels to a newer version for a special upgrade price. Before I upgrade my Parallels, I have two questions. My questions: 1. Can Parallels find my EXISTING older Mac OS partition, and run it under a newer OS? I don't want to figure out how to install an older OS I don't have an install DMG file for or any CDs/DVDs for. 2. Does Parallels do anything to the partition itself? Will I still be able to go to Preferences -> Startup Disk -> and change my bootup partition to the existing older Mac OS?
