In reply to Richard.

@Richard: Dorico is only officially supported on Windows 10 64-bit, but we have been running Dorico on Windows 7 64-bit, and on Windows 8.1 64-bit, and it runs fine on those operating systems. The issue is simply that we have limited support and testing resources, and we cannot qualify the software fully on every possible version of the operating system. So use Dorico on Windows 7 or Windows 8.1 at your own risk, but I do not anticipate that you will encounter any problems.