The software giant recently rolled out a new upgrade pop-up that prominently features big "Upgrade now" and "Upgrade tonight" buttons. This approach is more aggressive than before, and will very likely increase the conversion rate of people upgrading from Windows 7/8.x to Windows 10.
You can still dismiss the pop-up by clicking the X in the upper-right corner, but the new message is definitely less intuitive for less experienced PC users, as there's no longer a clear "no, thank you" option.
According to recent estimates, over 150 million PCs are now running Microsoft's Windows 10 operating system. If you're still using a previous-gen version of Windows, you still have seven months to upgrade to Windows 10 for free, although it wouldn't surprise me if Microsoft eventually extends the offer.