We use Thunderbird as an email client. To move it seamlessly from one computer to another Windows users may want to try this:
Update the T-bird version on the old computer to the same release to be used on the new computer — this will reformat the profile file(s) to the correct version.
Install T-bird to the new computer but don’t launch it when given the chance at the last step of the install.
On the new computer enter %appdata% in the Windows Search Box. In the directory that opens, select “Thunderbird” and then “Profiles.” Copy the name of the default profile file, then rename it with an x in front of the name.
On the old computer, copy the default profile (accessed the same way) to the transfer media. When it is finished copying, rename it to the same full name as the new computer’s T-bird profile file before you added the “x.”
Now simply copy this file into the same folder as the “x” file.
Start Thunderbird and verify all is well. For me this included sending/receiving a test email just to make sure I had the POP and SMTP servers connections I expected.
Once satisfied return to the folder and delete the “x” file.
But don’t delete the original profile folder from the old computer until you are truly satisfied all is well.
Validated on Thunderbird 7.01.