I'm told by some of my Scan125 users that Scan125 runs quite happily on a MAC but you have to use Bootcamp to boot Windows OS natively or use Parallels (? Fusion).
If you can't find/don't have a valid Windows install CD/License then you can, or used to be able to, use Windows 10 unactivated. After x days it starts to nag and after that some user customisation functions were not available and the lower right corner of the screen is similarly watermarked.
See:
How Long Can You Use Windows 10 Without Activation?
I do not know if this W10 status still exists.
Failing that then there must be eBay/other W7/W8.1 licenses out there for next to no cost.