are familiar with the Registry Editor, navigate to and export;
NT\CurrentVersion\Windows Messaging Subsystem\Profiles\Outlook.
more info read this article : http://www.slipstick.com/outlook/config/how-to-backup-your-outlook-account-settings/
You can try above in case of Outlook not with Thunderbird. Thunderbird makes it very easy to back up all of your email and account information in a few clicks. There is no database or settings stored in the windows registry. It’s one folder that you may burn to CD, copy to your external HD, or save to an online backup service.
All your email and account settings are stored in 1 folder depending on your operating system simply copy that folder to external media and you’ve got all your mail backed. You bought a new computer? Simply copy the folder from your old computer to the same location on the new computer install Thunderbird and presto all your mail is restored!
On Windows 7 & Vista Thunderbird data is stored at: C:\Users\<user name>\AppData\Roaming\Thunderbird\
On Windows XP Thunderbird data is stored at: C:\Documents and Settings\<user name>\Application Data\Thunderbird\
On Linux Thunderbird data is stored at: /home/<user name>/.thunderbird/
On OSX Thunderbird data is stored at: ~/Library/Thunderbird
Best thing is because Thunderbird is open source you can just copy your Thunderbird folder over from windows and rename it .Thunderbird and have all your mail and customization carried over.
Make sure that you should enable the “Show Hidden Files & Folder” option from Folder Option in your PC.