No it wasn't. I did the free upgrade from a copy of Windows 7 I "found", and I built my own PC from a parts store. So I've got a legit registered copy of Windows 10 running on my main PC, but I never actually gave Microsoft a dime.
Other than laptops I've never bought a store-built PC, nor have I ever purchased or owned any legit Windows install disks. So I understand that the copy of Windows I run on my main PC isn't "free" but it ain't me who paid for the thing. My guess is that Microsoft doesn't put any DRM on their disks because they want Windows to be ubiquitous even if it gets pirated, also backed up by their willingness to upgrade pirated Win 7 to legit Win 10 entirely for free. They got big on desktops basically by giving the operating system more or less for free to OEM manufacturers. Like, you can't really get a laptop without the OS any cheaper than one with Windows on it and the same specs, can you now? Their main source of revenue is actually the corporate sector, it's never been consumer desktops, and this actually explains the widespread Bill Gates = Evil Bogeyman thing that was big in the mainstream media. Microsoft was/is bleeding the corporates of money and they know he had them by the balls, so Gates was fair game for the corporate media to take jabs at. The reason they hated him is that the same class of people who run the media, white collar office/corporate was his target market in which he had a near-monopoly.