Microsoft quickly issued a statement saying that the checking of the upgrade's Optional item "was a mistake."
"My guess is that [people now reporting unexpected upgrades have PCs that] are configured both to install Windows updates automatically and they also have the 'Give me recommended updates the same way I receive important updates' checked in Windows Update settings," Mayfield said.
Another possibility, said Mayfield, was that users who had previously set Windows 7 or 8.1 to not update automatically -- thus stymying a Windows 10 upgrade -- had had those settings changed by Microsoft. "I have had reports from three different users in the past week who've seen their Windows Update settings change from one of the three options that don't automatically install updates to 'install updates automatically,'" Mayfield noted.
Microsoft regularly updates Windows Update, and in the past, some of those updates have switched user-selected settings or pre-checked optional updates. Recent refreshes of Windows Update -- the latest was issued on March 8 for Windows 7 and Windows 8.1 -- may have done just that, triggering the automatic upgrades on PCs that should have been immune from a forced migration.
What remains unclear is whether the behavior -- specifically, the completely-hands-off Windows 10 upgrade -- reported by users was by design or another goof.
The Redmond, Wash. company declined to clarify. When asked to explain why users were seeing their PCs upgraded without a chance to decline, or were trapped in an endless loop that eventually forced them to acquiesce to the upgrade in order to regain control of their machines, a Microsoft spokesman provided a boilerplate statement that repeated what the company has said before about Windows 10 upgrades.
"[As] we shared in late October on the Windows Blog, we are committed to making it easy for our Windows 7 and Windows 8.1 customers to upgrade to Windows 10," the spokesman said. "As stated in that post, we have updated the upgrade experience to make it easier for customers to schedule a time for their upgrade to take place."
In the referenced blog post of Oct. 29, 2015, Terry Myerson, who leads Microsoft's operating systems and devices group, announced that Windows Update would be used to serve Windows 10 upgrades to eligible consumer systems. The practice was extended in January to business PCs not managed by an IT staff.
Back in October, Myerson promised that users would be able to block a Windows 10 upgrade without resorting to fiddling with the registry. "You can specify that you no longer want to receive notifications of the Windows 10 upgrade through the Windows 7 or Windows 8.1 settings pages," he said at the time.
Sign up for CIO Asia eNewsletters.