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Golden rule to follow when upgrading from an old version of TB i.e. 78.x.x to a new major one i.e. 91.x.x

Hi Lampros,

Many thanks for your experience driven advice. (here is the link to your post in case others find it helpful https://support.mozilla.org/en-US/questions/1349565)

And I'm really sorry I'm so late in my response.

And I see Matt is suggesting it may not be necessary.

I'm still as confused as ever.

I think I should clarify a few points.

1) As mentioned, I will be changing 'bitness' from 32 bit to 64 bit. 2) I'm not as concerned about Calendar as I will recover later from from google. 3) I have already exported Contacts.

So... Should I uninstall TBird and all folders and files of it first? Or Should I just take a deep breath and update as-is?

Again, many thanks!

Mike.

First backup calendars and contacts. If you have imap accounts emails should be on the server. If in case backup local kept emails files using import export tools ng. Delete Thunderbird folders in App data Local and app data Roaming folders. Uninstall Thunderbird. Install TB91 Create a profile. Create your accounts. Create any necessary folders in Local folders (acc. to your needs) Install necessary add-ons. Restore by importing your calendars. Restore local kept emails (using import export tools ng add-on). You will see that you will not face any problem in the future. Same steps should be followed when TB developers will release another big new release.

Hi everyone!

I updated Thunderbird from version 78.1.3 32-bit to 91.3.0 64-bit on two of my Win 7 machines and will soon update the other machines.

I used a combination of recommendations from Lampros, scg, plus my own twist.

Much of what I did was likely unnecessary, but it all worked out very good.

Here is what I did... 1) Backed-up my address book and calendars. 2) Uninstalled the Calendar and the "Provider for Google Calendar addon". 3) Made a full copy of the "Thunderbird" folder in "C:\Users\MYUSERNAME\AppData\Roaming\". I knew I would need the "Profile" folder contained within, but I wanted everything just in case. 4) Uninstalled Thunderbird and deleted the "Mozilla Thunderbird" folder in "C:\Program Files (x86)" and in "C:\Users\MYUSERNAME\AppData\Roaming\". 5) Flamesuit On – Ran ccleaner registry cleaner twice, the first run left two files that were related to Thunderbird and IMAP, but I don't recall their name. 6) Rebooted the PC and installed Thunderbird 91.3.0 64-bit from a previously saved download. 7) Shut down Thunderbird. 8) Copied all files from inside the "Profile" folder from my previously saved "Thunderbird" folder. 9) Pasted them into the new "Profile" folder. (for some reason there were two profile folders, xxxxx.default.release and xxxxxx.default. I pasted into the xxxxxx.default because the .release one was loaded with important looking files) I did have one file conflict which I opted to "copy and replace". 10) Used the Windows "run" command for "thunderbird.exe -p" to open the Thunderbird profiles chooser. I clicked the "default" user " (remember it now holds all my previous profile files). I also ticked the choice for "Use the selected profile without asking at startup" option. If I ever create another user or profile I will un-check that option. 11) I then installed and linked my Google Calendar without the "Provider for Google Calendar" addon. (Remember I had intentionally un-installed Calendar before I saved my old Profile, because I didn't want to have any conflict leftover from the addon that I now don't use)

Yay!

All of my emails and folders are fine.

All of my Calendar events and settings are fine.

My address book was already in the profile, so there was no need re-import it.

I am so happy I could $#!t.

One curiosity and one unexpected glitch.

1) Mozilla Thunderbird installed into the 64-bit "Program Files" folder instead of the 32-bit "Program Files (x86)" where it was before. I had anticipated it would install in the 32-bit folder as others said it would, but I am overjoyed that it installed in the 64-bit folder.

2) I had to re-install my "got mail" jingle for "new mail notification" on my second machine, because the saved contents of the saved "Profile" from the first machine had a version saved in a different path.

I got what I wanted, as "clean" an install as I could. I was really worried because of the major 'version' jump plus the 'bitness' change from 32-bit to 64-bit.

Many THANKS to all of you!

Mike.