Why not just let the software manage your upgrades? Help > about will identify the next update you need and download it. Unless you have done something to break the update process, that is the preferred method.

There has been many updates since v78. All of those major updates - v91, then v102, then v115, and so - have had various changes. Some of those changes involved format changes for files such as those used by address book.

It might seem a bit long winded, but it means you can get each stage done so it's in a state which the next update is ready to use. I would advise that you create a backup of your Thunderbird profile. if you use Windows OS and default location for storage then it will be here: C://Users/username/Appdata/Roaming/Thunderbird You must exit Thunderbird before you create the backup. See image below which shows you how to locate the 'Thunderbird' folder.

You would need to get a copy of that Thunderbird folder and paste it somewhere appropriate to act as a backup eg: on D: Drive or create a folder on Desktop and call it 'TB-Backup' - in that folder create another folder which has the version number as folder name and put the copied 'Thunderbird' folder into that eg: 'TB-v78' folder.

After each update if everything is working ok - I would suggest you perform a backup again. In 'TB-Backup' create a new folder with the new version number eg: 'TB-v91' and put another copy of 'Thunderbird' folder into it. Repeat this until you get up to date. Assuming all is working ok. The last version will be whatever is current eg: 128.3.0 If all still ok create the last backup - then you can delete all the other backups and finally empty the Computer Recycle Bin.

When it comes to installing old versions, I'll suggest specific versions because a few gremlins were being ironed out when each new major version was first released, so these versions were the first ones which were released as an upgrade. Remember to uninstall just the Thunderbird program before installing new version.

Version 91.1.2

• http://ftp.mozilla.org/pub/thunderbird/releases/91.1.2/

Version 102.2.0

• http://ftp.mozilla.org/pub/thunderbird/releases/102.2.0/

Version 115.2.3

• http://ftp.mozilla.org/pub/thunderbird/releases/115.2.3/

When you use those links, you then need to click on appropriate OS eg: win64 Then choose your prefered language eg: en-GB for English British Finally click on the exe file link eg: Thunderbird Setup 91.1.2.exe to download.

Matt's advise is equally valid.

So you have two methods. But do create a backup - if something goes wrong at any stage, you will have a backup of the last working profile meaning if you lost eg: an address book then it can be recovered.

Many thanks for all of your swift responses. I will follow the Toad-Hall steps, really appreciate the detailed response. It sounds as though the Profile database should not need any specific export/import activity, I just need to constantly make the backups as a precautionary measure if I should ever need to revert to a prior version.

Lastly, I forgot to ask if the first step is actually to get to the latest level of v78 ? I am currently on v78.9 (32 bit), do I need to get to v78.14 ? I also intend to make the transition to 64bit along the way, perhaps I should do that as part of going to 78.14 ?

Thanks again to all the contributors.

re: do I need to get to v78.14 There were a few bug fixes and modifications the Ux in the versions up to 78.14 but nothing major. But doing an update to v78.14 should not be a problem.

re : I am currently on v78.9 (32 bit).... I also intend to make the transition to 64bit along the way,

I'm assuming you are using a Windows 64bit OS. Currently, your Thunderbird 32bit program is probably in this location:

• C://Program Files (x86)/Mozilla Thunderbird

I also have Windows 64bit OS. Some time ago I also used a 32bit Thunderbird. I now use 64bit Thunderbird. But....back when Thunderbird had just brought out the 64bit, if people had previously been using 32bit, some people had problems when they removed it and installed the 64bit version. The 64bit version got installed into C://Program Files (not Program Files (x86)) which was expected. But in many cases there were issues. So in those days, there was a temp situation where the 64bit update was auto installed into the place where you would expect a 32bit installation. It certainly confused me at the time. That may not occur now. It was never a problem for people people installing for the first time.

You have the choice. Completely remove the C://Program Files (x86)/Mozilla Thunderbird folder and let the install auto put into : C://Program Files/Mozilla Thunderbird and see how things go - you may find it all works ok. OR follow instructions to install into the same location as currently used - I did this.

It does not matter if Thunderbird runs from the old expected location. Indeed, mine still runs from the 32bit location and I've never had a problem.

If you decide to do the same as me - when removing the Thunderbird program -

• Access: C://Program Files (x86)/Mozilla Thunderbird folder
• Delete all the contents from the 'Mozilla Thunderbird' folder - so it's empty.
• Download the 64bit version
• When installing Thunderbird - you will get options - to install default or 'custom' - if required select 'custom'
• Choose the C://Program Files (x86)/Mozilla Thunderbird folder and then thunderbird gets installed in to the original location.

You could then repeat that action of installing into the original Mozilla Thunderbird folder. By the way, I'm now latest version, so get updates in normal way and they update auto in my selcted location. So I'm not constantly having to do that 'custom' install. It will only be necessary for you to do until you get up to date.

REmember to empty the computer 'Recycle Bin'.