Haha cool 95 is winning by a thin margin. I was a tiny little miss (like 4 or 5) when Windows 95 came out and we got one. And then it died and we didn't get a computer until like 2005 and I've been internet addicted ever since.
Whatever the earliest was, we had a big box computer like as soon as they came out. I remember getting a NickClick camera at some point when I was little and using the photo editing software... that was in the late 90's though and I know we had a computer for a while before that.
Windows XP on a Packard Bell computer from 2000 or something, which still works fine and it is pretty fast too. I can actually play minecraft on default settings with around 45fps. Now THAT is a good computer!