I beg to differ, I tried that approach a few years back with my folks, only to discover on my next visit a few months later that they went down to a local PC store and got Windows re-installed.
They never managed to get it working for their liking, it wasn't able to run the stuff their friends used to talk about or share via CD/DVD/USB sticks, and they did not wanted to bother me with "dumb" questions.
So I rather that they have Windows, go down to the local PC store when something isn't working as it should.
Of course you need to help them to alternatives, if they are not that tech-illiterate that they have very specific wishes for software.
It's been a while since I experienced people sharing software one discs by the way, it's been a while since I saw discs at all ;)
I do the same with acquaintances whom I sometimes sell secondhand gear, I don't want to do any support so they get Windows. For my father it's different, I can do support, plus he really appreciates and is willing to make sacrifices for, the privacy angle.