Hello, I have followed the instructions at https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer, and also tried several variations thereof - all without success. '''PROCEDURE:''' After each failed attempt, I uninstalled TB. The TB profile folder under %APPDATA% was also removed, and a new clean copy of TB installed, once 78.6.1 and once 78.0.1. The backup folder was '''copied''' via opening TB -> Help -> Troubleshooting Information -> Up three levels to "Thunderbird" -> Closing TB -> Copy "Thunderbird" -> Save to file. The backup folder was then '''installed''': 1. via -> Help -> Troubleshooting Information -> to the respective directories shown below, and, 2. when the above didn't work, a new clean install (after deleting TB from both "Programmes" and from "%APPDATA%") to the directories shown below. Nothing of the below resulted in the Profile and emails coming up when opening TB: '''"Thunderbird" folder:''' 1. Pasting the saved "Thunderbird" backup folder over the newly installed "Thunderbird" destination folder. 2. Emptying the newly installed "Thunderbird" destination folder first, then pasting the saved "Thunderbird" backup files/ folder into it. 3. Merging the contents of the newly installed "Thunderbird" destination folder with the contents from the saved "Thunderbird" backup files/ folder. '''"Thunderbird"/ "Profiles" folder:''' 4. Pasting the saved backup "Profiles" folder over the newly installed destination "Profiles" folder. 5. Emptying the newly installed destination "Profiles" folder first, then pasting the saved backup "Profiles" files/ folder into it. 6. Merging the newly installed destination "Profiles" folder with the saved backup "Profiles" files/ folder. '''"Thunderbird"/ "Profiles"/ "... default.release" folder:''' 7. Pasting the saved backup folder "hpaxv0u8.default-release" over the newly installed "…...default-release" folder (its name changed with each new TB install). 8. Emptying the newly installed destination folder "…..default-release" first, then pasting the saved backup files/ folders from "hpaxv0u8.default-release" into it. 9. Merging the newly installed destination folder "….default-release" with the contents with the "hpaxv0u8.default-release" backup folder. '''RESULT:''' Each time, the backup profile files/ folders are copied and visible in the respective newly installed directory. But on opening TB, the prompt comes back on asking to set up an email account. https://support.mozilla.org/en-US/questions/1289124?utm_campaign=questions-reply&utm_medium=email&utm_source=notification#answer-1318119 advises to “copy everything from the backup profile folder ... , delete everything from the target profile folder that opened in the pevious steps then paste into the now empty target folder." When I do that, TB is unable to start up. Error message: "Your Thunderbird profile cannot be loaded. It may be missing or inaccessible." '''NOTES:''' - The two TB versions were downloaded from https://archive.mozilla.org/pub/thunderbird/releases/78.6.1/win64/ and https://archive.mozilla.org/pub/thunderbird/releases/78.0.1/win64/. - The two TB versions were installed and removed nine (9) times each (as per the procedures described above). So a total of 18 failed attempts to transfer a backed-up profile. On the same PC as before, where TB had worked just fine: Windows 10, 64-bit. Wot to do? Many thanks.