Since they each have separate copies of the profile, you're pretty safe. I first suggest you rightclick on the desktop icons to see where each is installed. You mention 'windows apps' - did you install these from Microsoft or from Thunderbird? I encourage clicking help>troubleshootinginformation and then scrolling to 'profile folder' and clicking 'open folder' to verify the location of the profile in case you need to copy elsewhere . If the profile is at other than c:\users\<yourid>\appdata\roaming\thunderbird\profiles you probably installed from Microsoft. Once the profile locations are known, the next steps are usually straightforward.

Thanks David, appreciate you.

Both apps were installed using downloads from the Thunderbird site. Three years apart.

I see now that the original ESR version was placed in "C:\Program Files\Mozilla Thunderbird\thunderbird.exe" in December of 2022; while the newer Release I just installed wound up in "C:\Users\ME\AppData\Local\Mozilla Thunderbird\thunderbird.exe"

As I basically used the default options back in 2022 - and (according to the migration instructions), assumed that going with the defaults again would simply update ESR to Release. Not give me two releases.

Is it possible - that their decisions as to what the installer "defaults" should be - have changed in the past 3 years? That they felt there was no need to look in deprecated (but default) locations and alert me that I was about to get 2 different installs by my choices (those "choices" being to hit [Next] a bunch of times)?

That might sound angry, but I am actually curious how this would happen, as I don't feel like I fell outside the typical use case here ;-]

And I probably need to fix it too. I have 2 shortcuts now that open 2 Thunderbirds.

Please click help>troubleshootinginformation in latest version and post screenshot. It is looking to me like you installed from Microsoft, as thunderbird does not install there. My personal recommendation is to remove the Microsoft version as it's difficult to get help for it, and the help>troubleshootinginformation tips we provide don't work with the MS version. Just my opinion.

The screenshot is here, up to the point I ran out of screen to shoot. Let me know if you'd like more segments or perhaps the text dump.

This installation was executed from file Thunderbird Setup 141.0.exe, downloaded appx 5:56 PM PST on 8/5/2025 from this location:

https://www.thunderbird.net/en-US/download/release?utm_campaign=kb_release_channel&utm_medium=web&utm_source=sumo&utm_content=link_release

The original version may possibly have been installed via Microsoft's app store - after 3 years I don't remember. However, I cannot see on their overview page that they install the ESR version as an option.

Not sure what else to add here. If you need more I'm more than willing to provide it. Ultimately I just want to follow the best corrective action to wind up with one Thunderbird installed, preferably Release as suggested.

I think it's a great app and make it a point to donate every year or more.

Ok, I think I may have been wrong in thinking it's from MS. but this would be the one to uninstall. However, to be safe, I would first click to c:\users\<yourid>\appdata\roaming\thunderbird and copy that folder to a safe place prior to the uninstall. It should not need to be done, but it would be a safe step to do.

To confirm: By uninstalling "this one" I'll be removing the newer Release version app. This will leave me with the legacy ESR version I had before.

If so, then once this is done I'll be back in time and on square one: Thinking that I should migrate my ESR version over to the Release version. I can tend to that thought later...

Is this a correct understanding of your suggestion?

Yes, but there's no need to rush on this, if you're not sure. The ESR should be more stable with fewer updates, but slower in getting new features. And, I always to backups prior to any major change. Here are the basics for the standard install:

BACKUP

1. ensure thunderbird is not running
2. enter %appdata% in search window on task bar and press Enter key
3. this should open windows file explorer in Appdata\roaming folder
4. highlight the Thunderbird folder and copy to external media

RESTORE

1. ensure thunderbird is installed and NOT running
2. enter %appdata% in search window on task bar and press Enter key
3. you should be in Appdata\roaming folder , copy&paste the exported Thunderbird folder there. This may prompt to overwrite an existing folder of same name. allow it
4. start thunderbird and all should be there

So everything is good?

Well... yes and no ;-]

The cause of this post and thread is "resolved", in that I don't have two Thunderbirds installed any more. But the inspiration • for moving from ESR to Release was not fixed by doing it.

• Neither the original version - nor the newly installed one - would trigger any calendar event reminders; whether local or calDav types - most notably when the reminder was set for somewhere around 14~21 days or more in advance. I understand that this question record is not the place to debug this entirely different subject.

So I saved my profile to the NAS, removed all the Thunderbirds and installed BetterBird instead. The reminders came back again and have been working ever since.

I'm not sure - given any difference between the code in those branches - if there is a logical reason why this was the fix which worked for me... but it did.

AL