A quick techie post for anyone who, like me, objects to Microsoft sticking advertising for its next operating system in their notification area and all over their Windows Update screen.
If you have Windows 7 or 8 and have suddenly had an icon appear in the notification area which says 'Get Windows 10' when you hover over it then, as far as I can tell, this has appeared because of a 'recommended' windows update KB3035583. I got rid of it (and an associated splash screen in Windows Update itself) by uninstalling that update and then hiding it.
Do note that whilst this worked for me, you should use due diligence on your own computer. I take no responsibility for anything which may go wrong.
Edit: Somewhat annoyingly, KB3035583 appears to have unhidden itself and installed as part of July's patch-fest. I've uninstalled and hidden it again ... so far, so good. I'll have to watch August's patches more carefully.