The 64bit has been available for years, so I am guessing you may have been upgrading a 32bit version. I will assume you installed from thunderbird.net. If you installed from Microsoft let me know before doing anything. - for safety, make sure thunderbird s not running - enter %appdataS% in search box on windows tasks bar - that should open to the appdata\roaming directory - highlight the thunderbird folder and copy it to somewhere else for safety - now uninstall thunderbird - if it prompts to delete data, tell it NO - now install thunderbird from https://www.thunderbird.net/en-US/thunderbird/all/ Pick whether you want ESR or Monthly - start thunderbird. if it doesn't open to your accounts, just close and exit - do NOT try to fix - now take the backed up thunderbird folder - repeat the %appata% to task bar and when window opens to appdata\roaming, paste your thunderbird over the top of the existing thunderbird folder. you will be prompted for the overwrite. allow it - now start thunderbird and your accounts should be there

Hello and many thanks for such a fast response.

I can't recall where I installed it from but almost certainly thunderbird.net

I'm guessing the 'S' in appdata was just a typo? Thanks again Alan

Yes, a typo. :) if you had installed from MS, the locations of everything is different.

Hello David,

All seems fine thank you. With one exception , I seem to be missing a 3d email address (not critical) but have my main two address's and emails which is the important thing. Still not sure why I had a 32bit install in the first instance. Like to think the 64 bit version is more appropriate today. Hope there's no other lurking issue! Kind Regards, Alan

I'm glad it went well. The 3rd account is puzzling, as upgrades encompass the full profile, so all accounts should be accounted for. Good luck.