''It always STOPS when instructed to Close Thunderbird.'' Of course Thunderbird stops running when you exit/close Thunderbird. ''Can't go any further without starting again.'' That is wrong, you have not properly read and followed instructions and you really need to follow the instructions. You have to exit/close Thunderbird to stop it from running, so that you can get a copy of the Thunderbird folder that hold all the profile data etc. You have to close Thunderbird - stop it from running, so that all the session data and other files are correctly ready for you to copy. So as the information shows, you have Thunderbird running to start with and then use Thunderbird to get quick access to the 'profile name' folder that holds your profile information. This will open in a new Windows 'Explorer' window in this location: C:\Users\<Windows user name>\AppData\Roaming\Thunderbird\Profiles\'profile name' folder It will look similar to the image below. At this point you must exit/close Thunderbird to stop it running. Then, in the new Explorer window showing your profile data, you go up the directory three clicks to get to the 'Roaming' folder which holds the 'Thunderbird' folder. You will need to copy the 'Thunderbird' folder. Video and written form information: https://support.mozilla.org/en-US/kb/moving-thunderbird-data-to-a-new-computer