When my computer was repaired, Windows was reinstalled but I lost various programs, including Thunderbird. I had to reinstall it. I assume my data--my email database--was not erased,

That is a big if. Did the repair include replacing your hard disk? If that answer is yes, your mail is almost certainly gone. How was Windows reinstalled? There are multiple ways and some leave a windows.old folder which may have your mail in it. Others just flatten and pave over anything that was there.

As I recall, Windows was corrupted and had to be reinstalled. I don't recall a hardware problem. When I got my computer back, many of the apps had disappeared with reinstallation and there was an icon reading RemovedApps.html, listing the apps that were removed with reinstallation. There was one for Thunderbird.

I reinstalled Thunderbird, but if my emails were preserved, I don' t know where they would be. The Thunderbird help site has instructions for finding profiles, but that didn't help. I think I found a screen for the default profile, but I can't figure it out, and I don't know where the emails would be if they still exist.

In fact, I also don't know how to configure Thunderbird to download my email, as I use my own web site email address, but which is hosted by Earthlink.

As my email was for the most part never deleted from the Earthlink site (at least going back a fair ways), I could presumably download it all from scratch with a new profile, but then it wouldn't have been sorted into different folders as it was. And we're talking about hundreds of emails, most likely.

It was Thunderbird, version 128.5.2

I guess no one has anything else to add. In lieu of being able to locate my orphaned email on my hard drive with reinstalled Windows, I searched my external hard drives for backups which I thought I last did no earlier than 2024. But all I can find is a back up dated May 3, 2016, in a folder called 'Thunderbird', which contains the file 'profiles.ini' and the subfolder 'Profiles', which contains a further subfolder 'jzgqu2or.default', which contains everything else including the email folders. Thunderbird has of course changed in 9 years, but can I recover this profile? I would keep it separate from a new default profile.

Profiles on Windows are usually stored here: C:\Users\<YourUsername>\AppData\Roaming\Thunderbird\Profiles\

See if your latest profile is there.

You can restore your old profile by copying it to the directory specified above. To use it, use the Help menu > Troubleshooting information > about:profiles.

No back-up in the last nine years?!

Thanks for telling me where to look. Oddly, that file folder doesn't exist. So I wonder if that folder was wiped when Windows as reinstalled.

Also, when I look at the file directory and search it, I don't see any of these folders unless I type in the exact format, e.g. '\Users\<YourUsername>\AppData\'. I didn't even know such folders existed.

So, typing in this way works up to a point, but '....\Roaming' doesn't show up at all. \Users\<YourUsername>\AppData\Roaming\Thunderbird\Profiles -- nothing.

I am sure I backed up my data more recently, at least within the past year and a half, but I'm mystified. I wonder if instead of backing it up on an external hard drive, I put it on a laptop that is no longer usable. But that doesn't make sense.

Yeah, as Matt suspected might be the case, apparently your Thunderbird profile was wiped when Windows was re-installed.

Did you get Thunderbird from the Microsoft Store? Then look here: C:\Users\<YourUserName>\AppData\Local\Packages\MozillaThunderbird

Good luck finding a more recent back-up copy. Maybe the file path above helps you find it.

You can re-install Thunderbird and set up your account(s) again. You would have access to messages that are on the server. You would not have access to messages that you stored in local folders. If you find your local folders later, you can add them to your new profile then.