Linux

I upgraded from 7 to 10 right around when it released. Microsoft got me with the "Free upgrade offer".
Problem is, I had a very shitty ADSL connection, so when Windows Update started doing its thing, it would make it almost impossible to do anything else on the web.
There were many times I would turn the computer on to do something, only to be unable to load any webpage because Windows Update was eating all my bandwidth.
And to make things worse, Pausing updates, Active Hours and other controls only came out much later, early Win 10 had none of it. When it wanted to update you had basically no control over it. There were some registry hacks to disable updates, but those didn't really stick for some reason, so many times I applied one and thought the issue was fixed for good only to come back to my PC days later and face the same issue again.

Eventually I was like "Why the hell do I have to keep fighting my computer?". You can imagine the shock it was coming from Win 7.
I had tried Linux before all of this (Ubuntu 14.04) and while I did enjoy the experience I didn't stick with it, but I kept the idea in the back of my mind.
Some time later I setup a dual-boot, and year after year I relied less on Windows (and Linux kept getting better) until Linux became my daily driver. Fast forward to today: Windows isn't even a dual-boot install anymore, just a VM I barely use :)