Previously, I had my Parallels 10 on my HHD on my 2011 MacBook Pro. I upgraded to SSD in my Mac and after I restored my Mac on the SSD from time machine the VPM would not work. So, hoping to avoid the same problem in the future after a Time Machine Backup, I installed Parallels on an external drive. Every time I need Parallels I connect the external drive. Now, I had a software problem on my OS High Sierra. I backed up with Time Machine and then did a clean install of High Sierra onto my Mac SSD. That solved that software problem. However, when I try to launch Parallels after attaching the external drive, a drop down appears with the following: Parallels Desktop Cannot Be Started. Please Reinstall Parallels Desktop and Try Again. If the problem persists, contact the Parallels support team for assistance. Problem ID:15431. Needless to say, my solution failed I don't want to reinstall the program again. Won't this mean IO lose all my prior installed applications and data files in Windows in Parallels? Any suggestions greatly appreciated for my problem now and for avoiding this restoration problem after using Time Machine. Thanks