The free Windows 10 upgrade has been changed from an optional upgrade to a recommended upgrade. The upgrade could automatically start installing itself when Windows Update next runs.
In a blog post in October last year, it was announced “Early next year, we expect to be re-categorizing Windows 10 as a “Recommended Update.” The automatic updating came in effect on February 1. This only affects users who have enabled ‘Give me recommended updates the same way I receive important updates.’ in Windows Update settings. Microsoft made this change to make the upgrade as easy as possible for users who reserved their upgrade, but are yet to schedule it.
For any user who might accidentally stumble into this automatic upgrade, they have 1 month to rollback the upgrade to their previous version. But for users still holding off on upgrading for any reason, the 1 year period to upgrade to Windows 10 for free is coming to an end in the next few months.