Here's how I do it when transferring all my TB settings from one computer to another. First, take note that the "appdata" folder is a hidden folder. So in Explorer you'll need to select VIEW then but a checkmark next to "Show Hidden Files". 1. On the source computer copy the following folders and their contents to a USB drive. C:\Users\<loginname>\appdata\local\Thunderbird C:\Users\<loginname>\appdata\Roaming\Thunderbird 2. On the new computer, install the TB Program. When it starts and request account information, click CANCEL, then click SET AS DEFAULT. 3. Exit the TB program. 4. on the new installation, go to C:\Users\<loginname>\AppData\Local and delete the Thunderbird directory. Then copy your backup of that directory from the USB drive to this location. Do the same for the ....\Roaming directory. 5. Reboot the computer. (THIS IS IMPORTANT!) 6. Now start the thunderbird program and everything should be there.