Something to watch out for if you don't want to upgrade to Windows 10
just yet...

My system: Windows 8.1 Pro
I have not yet reserved my Windows 10 upgrade

In Windows Update's "Optional" tab, there is an optional update
"Upgrade to Windows 10 Pro". Unlike other optional updates, this
one is automatically selected.

If you only look at the "Important" tab before clicking install, you
may get an update you were not expecting.


--
Kind regards
Ralph