Microsoft has launched the final push in its nine-and-a-half-month upgrade offensive against consumers and businesses running Windows 7 and Windows 8.1.

Last week, Microsoft switched the automatically-offered Windows 10 upgrade to a "Recommended" download that in turn scheduled the upgrade process unless the user interfered.

"As we shared in October, Windows 10 will be offered as a 'Recommended' update for Windows 7 and 8.1 customers whose Windows Update settings are configured to accept 'Recommended' updates," a Microsoft spokesman said Friday in an email reply to questions.

Those questions were spurred by reports from Computerworld readers, who said that they'd again been offered an upgrade after months of either ignoring the campaign or dodging the transmutation of their PCs from Windows 7 or 8.1 to 10.

In February, Microsoft kicked off the "Recommended" phase of its long-stated strategy to convince, coax and pester users into upgrading to Windows 10. At the time, the Redmond, Wash. company confirmed that it had begun pre-selecting the upgrade as a Recommended update delivered through the Windows Update service. But it also said that the shift to Recommended would "roll out in a phased approach," signaling that the migration would take weeks or months.

In Windows Update, a Recommended update is one that is automatically downloaded and installed -- no user assistance required -- on PCs whose owners have not changed the default behavior of the service.

Microsoft originally announced in October 2015 that it planned to use Windows Update, the operating system's default security maintenance service, to automatically send the upgrade to PCs.

Also last week, Microsoft expanded a long-existing support document that details what users see when the Get Windows 10 (GSX) app -- which Microsoft planted on millions of PCs last spring and has refreshed and reinstalled many times since on those systems -- schedules the upgrade and how people can cancel the process before it starts.

That scheduling is not new -- a search provider cache of that page still available on Friday showed it had been part of the push since at least March -- but the revised document was more detailed as well as more forthcoming about how the upgrade is triggered.

According to both the latest and the previous versions of the support document, the upgrade and its scheduled implementation is approved when the user either clicks the "OK" button or the "X" in the upper right corner of the notification.

"If you click on OK or on the red 'X', you're all set for the upgrade and there is nothing further to do," the document stated. The "X" Microsoft mentioned is one way to close a window in Windows.

But Microsoft's interpretation of clicking the X is contrary to decades of practice in windowed user interfaces (UIs) and normal user expectations: To users, shutting a window by clicking the X tells the OS to remove the notification or application frame without expressing an opinion, selecting an option or calling up an operation.

Instead, Microsoft equates closing the window with approving the scheduled upgrade.

Microsoft has applied some unusual stratagems in its efforts to get customers to upgrade to Windows 10, but this behavior is among its most aggressive simply because it is deceptive in the context of normal Windows UI behavior.

In fact, it's very likely that many of the accounts -- and they have been widespread -- that the proffered Windows 10 upgrade began without user approval can be traced to this strange interpretation by Microsoft. Thinking that by clicking the X they were rejecting the notification, or at least ignoring it, users instead were actually authorizing the upgrade.

When the upgrade began later, they professed they had not approved it, not remembering an explicit affirmation, when in reality they had -- under Microsoft's rules -- given the green light.

The free Windows 10 upgrade offer is to expire on July 29.