When you launch TB 68 64-bit, select Help/Troubleshooting Information, click about:profiles. Do you see a profile ending in .default, and if so, can you click the button 'Set as default profile' for that profile?

The directions provided by sfhowes is the ideal solution, thank-you. (Surprisingly easy when you know how!)

This is about T'bird 32 to 64 importation, but I have old emails from Eudora which still offers a 32 bit app, but T'bird won't open it & import it. I'm told by a Support.com tech I should ask here what to do to bring it to my new (WIN10, so 64 bit) computer.

LoiS said

This is about T'bird 32 to 64 importation, but I have old emails from Eudora which still offers a 32 bit app, but T'bird won't open it & import it. I'm told by a Support.com tech I should ask here what to do to bring it to my new (WIN10, so 64 bit) computer.

You might be able to import Eudora data with an older version of TB, and if that's successful, just install the latest TB over the existing setup. I would stay with the 32-bit version of TB; the 64-bit version is relatively new, and doesn't offer any significant performance advantages.

If you have the 64-bit version, just uninstall it, install the old version, do the import, then install the latest 32-bit TB.

https://support.mozilla.org/en-US/questions/1263977

Hi, I am surprised the later version doesn't have advantages. Beyond that, I've just gone through Olympic-style contortions putting all that came from 2005 into the latest TB. My concern (& that of the tech advisor) is that removing the 64-bit will then mean re-tracing all the steps we went through to get it. I don't know that I can re-trace those steps in the limited time remaining to finish my agreement with Support.com. Is there a safe way to clone it, somehow save it before removing it?

Uninstalling TB won't affect your data, which is stored in a separate folder, the profile folder. The installer for all versions is available here.

If you backup the Thunderbird folder, located at: C:\Users\username\AppData\Roaming\Thunderbird

that includes all user data, accounts, mail, contacts settings etc. that are necessary to restore to an existing computer, or copy to another computer.

But if you already have the latest TB 64-bit, there is no urgency as far as replacing it with the 32-bit version. Both will read the same profile folder.

Sorry to be so persistent, but now that my backup is made, I'm ready to install a 32-bit version, but can't tell what one to select on that monstrously long list of versions. Suggestions, Please!

I'm told I need the installer for whatever version. I believe version 17 for WIN32 is what I need but clicking https://archive.mozilla.org/pub/thunderbird/releases/17.0/ doesn't take me to an installer. There's another long list. Is https://archive.mozilla.org/pub/thunderbird/releases/17.0/win32/hy-AM/ what I need? I'm in the U.S. & thinking the AM is code for America. If so is that the installer?

The US English installer for TB 17.0.8 is here:

https://archive.mozilla.org/pub/thunderbird/releases/17.0.8/win32/en-US/

After the Eudora data is imported to TB 17, you can get the 32-bit installer for TB 68 here:

https://archive.mozilla.org/pub/thunderbird/releases/68.4.2/win32/en-US/

Woops! should be en-us not hy-am.

Index of /pub/thunderbird/releases/17.0/win32/en-US/

I have found this isn't going to bring new data from my old Eudora emails. As a result I am closing this. Maybe it will help somebody else. I do want to thank you for your help.

oops! should be en-us not hy-am