Sorry about the misunderstanding ... to operate the downloaded or CD version your OS must be up to the task ... if it is not then you cannot use that product ... instead you would need to log in and use the ONLINE version instead.
TurboTax 2017 Minimum System Requirements
Windows:
https://ttlc.intuit.com/questions/1901571-turbotax-for-windows-minimum-system-requirements
Mac:
https://ttlc.intuit.com/questions/1899173-turbotax-for-mac-minimum-system-requirements
