I am very sorry to hear about this Rik1968. Your iPhone 6s was updated to iOS 10.2 when incompatibility struck, is that correct? (We were originally under the impression that even 10.0 couldn't be supported using iTunes 12.1.3 on Vista, but apparently that wasn't precisely correct.) The first version of iTunes that did not support Vista or XP was actually 12.2.0, released on June 30, 2015. It's a minor miracle that version 12.1.3 was able to get you as far as it did. By the way, iCloud is a backup option that would not require a new PC.
I also have a Vista PC that I am very fond of, and "find it more than a little galling" that companies like Apple and Google are ending support for Vista even quicker than Microsoft. On the other hand, there will be no more security updates for Windows Vista after April 11 (and as you probably know, those Windows updates have been surprisingly hard to get for quite some time now), and it sounds like your collection of Apple devices is far more valuable than your old PC. Sooner or later, you will need a new PC.