If you use the following website:So it has taken a little over four years for Windows 10 to almost reach 50%, and they were even giving it away for free. This really doesn't seem like something to brag about.
http://gs.statcounter.com/windows-version-market-share/desktop/worldwide/#monthly-200901-201206
You can see that Windows 7 took a little under 3 years to reach 50% market share, and over the same period of time, WinXP's share went from 75% to 38%. I would bet that this was in no small part due to awfulness that was Vista. Now look at the same for Windows 8.1 and compare it to the launch of Win10:
http://gs.statcounter.com/windows-version-market-share/desktop/worldwide/#monthly-201310-201710
Win10 went from nothing to 42% in two years, and that's competing against WinXP, Win7, Win8.1. Yes, it took another two years to reach 50% but the initial share grab was significant.