Not "all" if you mean it literally. .NET came much later than Windows - maybe post-Win NT as well as post-Win 2K - others who know better can probably correct me or give a more precise date.
I remember meeting and talking with (or rather he did more of the talking) a senior Microsoft software engineer who was involved in the first .NET version, and he was telling me stuff about it. He may not have used the term .NET (can't remember), but I remember him saying that it used XML throughout (and also a lot of other stuff about its advantages). Very enthusiastic about it, he was. It was only some time later that I realized that what was now called .NET, was the same as what he had been referring to in his talk with me.
Also, Turbo Delphi Explorer (which was a stripped-down version of Delphi 6), came in two versions - the plain Win 32 version (non-.NET) and the .NET version. I remember, because I installed and used it some. Here's a blog post about a small utility I wrote with it (screenshot of the clock not there now, sorry):
http://jugad2.blogspot.in/2010/08/digital-clock-v10-in-3-lin...