Re: pushing a free upgrade
neither xp, nor vista, nor windows 7 ever managed these numbers. For perspective, 7, the best success story so far, managed 60M sales after 60 days. Windows 10 is not technically a month old. And this time they are counting "installs", not sales. Sales mean: sales to dell or OEMs which buy in bulk and still have to find their way to a store and turn into a consumer purchase.
So in fact 10 is MUCH more successful than anything MS has ever released because they haven't even talked sales (remember, windows 10 is free to upgrade, not OEMs on higher end PCs).
I imagine if they added channel sales plus upgrades, they'd easily clock 100M. unprecedented.