You can do it in different ways http://kb.mozillazine.org/Moving_your_profile_folder If you can access TB open ''troubleshooting information'' (under help or three-bars-icon /help) and click on ''open folder'' that will open a explorer-window at your profile EXIT TB If you cant open TB use explorer to go to your profile. That should be on ''%appdata%\Thunderbird\profiles\"some-letters.default'' (Using %appdata% will put you straight on to C:\users\"your Win-user"\appdata\roaming\) You need to see hidden files. Copy everything in here to a safe place ( card/memory stick/ extern usb-drive /cloud) I would add that other users have their own profile under their username or as a second profile under your .....\profiles.