Hmm, I am 64 but I sometimes feel like 100 and agree with everything Altoid said!

If you want to change your dad's system, rather give him an additional system, like an ultra fine resolution laptop from Apple. Any Apple lappy from the last ten years will do.  The reason I suggest Apple is that they are very good for people with failing eyesight.  As you get older you have more and more junk floating in your eyes and dim spots etc. and your short term memory gets bad, which makes it super annoying when a UI suddenly changes.  Maybe in a few weeks you will see him using the new one only and then you can recycle the old one.

I had cancer and the treatment affected my memory in subtle ways for a year or so and it recently started to recover, so I have much sympathy for old geezers now!