This surprises me. My experience has been that the Thunderbird updater won't suggest a version that's incompatible with the OS. Specifically, the latest version that runs on Windows 7 is 115.18.0. On my Win7 computer, when I check for Thunderbird updates, it always says that it's up to date. Also, if I try to install a later version than that, the installation stops with the error message, "Sorry, Thunderbird can't be installed. This version of Thunderbird requires Microsoft Windows 10 x64 or newer."

What version were you previously running and what did you get updated to?

When I now try to run thunderbird.exe I get the following: "C:/Program Files/Mozilla Thunderbird/thunderbird.exe is not a valid Win32 application."

As the executable can't run, is there a way to retrieve the version numbers somewhere in the Program Files?

This executable was auto installed at 9:44 PDT today (10/32/2025). I don't know the version numbers, but it looks like the last update was 5/12/2024.

You can find the version by locating the file "C:/Program Files/Mozilla Thunderbird/thunderbird.exe" with Windows Explorer by right-clicking on it. Then look at the "Details" tab and then "Product Version".

Yours is the 64-bit version of Windows 7, isn't it?

The danger of downgrading from a later to an earlier version is that the later version may have changed something in your profile that makes it incompatible with the earlier version. However, it sounds like you were never able to even start the new version, so your profile should be intact. That's a good thing. You may be able to just uninstall the later version and re-install the older, preferred version. But let's find out what's currently installed.

Eventually you will want to install the last Windows 7-compatible version, 115.18.0esr. You can get that here (assuming you want the US English version):

https://releases.mozilla.org/pub/thunderbird/releases/115.18.0/linux-x86_64/en-US/

I am very old school, running a 32 bit Win7 OS. The "Properties" on the executable gave me lots of information.

"Details"

 Product version 128.14.0
 Modified 10/31/2025 9:44 am

"Previous Versions"

 Previous Version
 thun 1/16/2025 8:35 am
 115.18.0 (32-bit)

The latter found in the restore point. I double clicked of that entry and it ran, abit without any libraries or data files as it isn't installed. I really really want it back proper with access to my old emails.

Can you install the last version for 32-bit W7?

https://archive.mozilla.org/pub/thunderbird/releases/115.18.0/win32/

It's Halloween - I'll pick this up tomorrow - thanks

Hi Lin. As I understand I should "reinstall" version 115.18.0 (32-bit) and that should work. - Do I first "uninstall" thunderbird first? or should I just "install" 115.18.0 (32-bit) over existing? - As a reminder previously I did a Windows restore, this didn't work, so I undid the restore. - Is there some backup I should do first? I really, really want to keep access ti my inbox content.

I would first make a backup copy of your profile, the default location of which can be found at

C:\Users\<your Windows profile name>\AppData\Roaming\Thunderbird\Profiles

If you see more than one profile folder, peek inside each folder and choose the one with the latest file dates.

Then, considering that you seem to have a botched installation of an incompatible version, I would uninstall it completely. At some point it may ask you if you want to delete your data - you don't, but you have a backup copy if you do.

Assuming the uninstall proceeds successfuly, reboot the computer and install the latest version that's compatible with Windows 7 32-bit, which can be found at the link that sfhowes cited above.

I uninstalled Thunderbird, then rebooted - no apparent problem. How do I install 115.18.0? I clicked on link above link and got to a directory with two files as follows: File thunderbird-115.18.0.tar.bz2 77M 10-Jun-2025 20:44 File thunderbird-115.18.0.tar.bz2.asc 833 10-Jun-2025 20:44. Do I click one of these?

Sorry, I should have checked the link - it's incomplete. Go here (assuming you want the US English version):

https://archive.mozilla.org/pub/thunderbird/releases/115.18.0/win32/en-US/

and get the file "Thunderbird Setup 115.18.0.exe".

I uninstalled Thunderbird, then rebooted - no apparent problem. How do I install 115.18.0? I clicked on link above link and got to a directory with two files as follows: File thunderbird-115.18.0.tar.bz2 77M 10-Jun-2025 20:44 File thunderbird-115.18.0.tar.bz2.asc 833 10-Jun-2025 20:44. Do I click one of these?

The tar.bz2 in that folder is for 64-bit Linux and not Windows.

Well, I must say I am glad I asked :) Success! It installed swiftly and my mail is all there and intact. Thank you so much for your guidance.

Last question. I never, ever want another auto update. How can I deselect the auto update setting?

Glad to hear you're back in the saddle!

To turn off automatic updates, go to Tools | Settings | General | Updates and select the option "Check for updates, but let me choose whether to install them". This way, Thunderbird will let you know if an update is available, but you have to explicitly OK it install the update. But since this version is the end of the line for Windows 7, you won't get any more notices.

Very good. This issue is solved, except you might want to submit a bug report to the update team. Checks should exist such that an incompatible update is never pushed in the first place. Thanks for your help!

I'm very familiar with the update rules which prevent such things, so I suspect you got the incorrect update from some mechanism other than Thunderbird - perhaps some software maintenance tool.

Hi Wayne - This is a personal PC installation. There are no installed software maintenance tools that were intentionally installed. The aberrant update files are all dated 10/32/2025 at 9:44am PDT. I did make a copy of the entire c:/Program Files\Mozilla Thunderbird" directory before I uninstalled. If there is anything in there you would like to see let me know.