A while ago I realized that people won’t listen to me when I tell them about the evil monopoly Microsoft ignoring standards and conventions, so I started to just force them to use OSS, e.g. Firefox.
That is, when they ask me to fix their computer, or even when I’m merely using it, I install Firefox and set it as default browser! If I don’t forget to install all the Plugins, they merely notice the difference.
But one time I went too far – I installed Linux on a friend’s PC while he was out for lunch; he wasn’t all that happy :-) (Of course on an unused second partition, no data was lost – he would have killed me anyway.)