Microsoft is on everyone's hate-list again, because closing the Windows 10 upgrade dialogue without explicitly cancelling an installation leaves the upgrade on the schedule.
This Knowledge Base article explains that the only way to cancel the upgrade is to click on the “change upgrade schedule” link.
“If you click on OK or on the red 'X', you’re all set for the upgrade and there is nothing further to do“, Redmond explains.
Somehow, the article fails to explain why closing the dialogue (clicking the invitingly red “x” at the top right) doesn't do what the user expects, but rather, it schedules the upgrade.
That little bit of sneakiness will get it more downloads of Windows 10, but probably at the cost of yet more criticism. ®
The only way to cancel the upgrade: closing the dialogue schedules it.