Question: iTunes 12.2 has dropped Windows Vista Support
I know Windows Vista is about 3% of the world PC market. But as the MAC is only 8% it and I highly doubt Apple has any plans to drop support of iTunes on the MAC anytime soon. Dropping support for Vista is silly as it is still a supported Operating System.
So Apple please re-consider because I highly doubt you need ti change any code other then the part that checks what version of OS you have installed before you it starts the install.