How do I turn off the end of support banner in office 2010 permanently? (Office 2010, Windows)

HKCU is programmers abbreviation for HKey_Current_User

• H=Hive (a collection of registry entries)
• K= Key
• CU = Current User

That is the registry key currently being used. That is where the OS looks to find registry settings. If you use the OS to make changes, this is where the changes are written

The .Default user is the template MS uses to create new user keys.  The rest of the keys under HKey_Users are generated by Windows as new userids are created.  They are typically MS cryptic

This article provides some information about the subkeys under HKCU:

https://www.lifewire.com/hkey-current-user-2625901

There are many useful additional links about the registry at the bottom of this page.

When you sign in to Windows with a specific Windows userid, that tells Windows which specific sub key under HKey_Users to copy from into HKCU.

At the end of the Windows session, part of the shut down process copies the values under HKCU to the specific

HKey_Users subkey.

One of the sub keys under HK_Users is for the admin account (I think it is S-1-5-18 on all machines).

This article tells you how to identify the specific user/user ID for each of the HK_Users subkeys

https://support.esri.com/en/technical-article/000010572

I'm guessing the 2 keys that are in my registry ( "0:en-us" and "1:en-us") are for Excel and Word since those are the only products I use. Perhaps those who use Powerpoint, Accesss, etc would have more keys? 

That is as good a guess as any. But since this is an Office wide setting, "logically" I would expect that one key would be enough for the whole suite. But who knows what MS is thinking.

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As for updates, "Officially", yes all updates end on Oct 13. But unofficially people have noticed a few updates to 2007 and Win7 after they went End of Life. In a couple of very well publicized, generally used hacks MS has admitted creating updates for EOL programs, but it is very much the exception. Not something EOL uses can count on.

I thought it wouldn't hurt since support is ending anyway so there won't be any more updates to Office 2010?

And also turn this setting off:

Roshanlal, why do you suggest this? It has nothing to do with the message in question. Any changes MS would make to the registry for Office will come through with or without this setting. Personally, I prefer to keep it on to simplify keeping Office up to date.

I'm not sure I understood the 1st part. But as to seeing the whole key missing, would it help if most of the privacy options are unchecked in Office? As in the following: