Hi Mark. I'm Greg, an installation specialist and 10 year Windows MVP here to help you.
Yes, popups from the System Tray are usually legit. It's popups from Web pages that would be suspect in this case.
It means you have an older version that's about to lose Support. You should always have the latest version of Windows 10 that your PC can run. Let's get that installed now while I'm here to help you smooth out any rough edges.
I would manually upgrade to the latest version 1903 by opening the Media Creation Tool from this link: http://windows.microsoft.com/en-us/windows-10/m..., choose Download Tool Now, then open the tool and choose Upgrade This PC Now. This saves your files, apps and most settings in place, is the most stable method to change versions, brings your Updates current, resolves most problems.
If any problems report back the verbatim error and number, then continue with these steps for overcoming Version Upgrade problems: http://answers.microsoft.com/en-us/windows/wiki...
If the Version has problems I will work with you to try to resolve them. If the problems are intractable, you have ten days to roll it back in Recovery settings.
Most problems are resolved by doing this gold standard Clean Install which should get you past all difficulties as it has millions of others who have followed the steps in this link and never come back to report another problem: http://answers.microsoft.com/en-us/windows/wiki... . So read it over and see if its something you want to learn to do.
I hope this helps. Feel free to ask back any questions and keep me posted. If you'll wait to rate whether my post helped you, I will keep working with you until it's resolved.