Microsoft's getting ready for the more aggressive upgrade phase of Windows 10 – when the new OS will show up first as optional, and then as recommended download in Windows Update – so the company has recently made some changes to Windows 7 and 8.1 PCs to make sure that more computers get it.

Basically, settings on PCs that were previously configured not to receive the upgrade to Windows 10 have been reset and it appears that one of the updates that Microsoft deployed on Windows 7 and 8.1 PCs keeps checking every day to make sure that no other changes are made to this behavior.

Update being re-offered several times

The information comes from the creator of GWX Control Panel, an application developed to block the upgrade to Windows 10.

"Over Thanksgiving weekend I started getting reports that the Windows Update 'AllowOSUpgrade' setting was getting flipped back on on a number of peoples' PCs, and it keeps re-setting itself at least once a day if they switch it back off," Josh Mayfield was quoted as saying by CW.

In other words Windows 7 and 8.1 computers can now easily receive the upgrade to Windows 10 and for the moment, there doesn't seem to be any other way to stop this from happening than to manually refuse the new OS.

It's all being made through recently-shipped Windows updates for older versions, and according to Mayfield, the very same update is being re-offered again and again.

"Microsoft has released this update several times," Mayfield continued. "It doesn't change the name of the update, but every version is new, with new binary files."

Starting in early 2016, seeing Windows 10 in Windows Update will be quite normal, as Microsoft changes its strategy and makes it an optional update for everyone. At a later time, the upgrade will become “recommended update,” so it becomes harder to avoid installing Windows 10 if you really wish to keep your computer fully patched.