Hi There may be more than the address book missing. You mentioned you tried copying 'the entire folder' - but which folder? Did you use the method to copy the entire profile over and then set Thunderbird to open the desired profile? https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data If you really do want to transfer only the address book - the file names changed from .mab to .sqlite around version 78. Assuming yours has been updating you should be lookingin Profile folder for abook.sqlite and history.sqlite. This previous answer from Toad-Hall walks through some options to recover the address book files. https://support.mozilla.org/en-US/questions/1358888

Agnes- Thanks for the help. However, I am unable to find my profile on the old hard drive. I searched for both .sqlite and .mab. I'll take a look at the Toad-Hall response, but I'd appreciate any further instructions from you. Tom

Hi Using information from the 'Profiles where Thunderbird stores user data' article - Thunderbird stores the program in one place and the user settings and mail in another, so be aware not to look in the Program Files - Mozilla ... folders. You need to be sure you are looking in "C:\Users\<username>\AppData\Roaming\Thunderbird\Profiles\" where C is the drive (probably not C if you are accessing the old drive from the new computer), and <username> would be the username from your old computer. You will need to substitute the drive letter and user name to match your old rescued drive. Don't try %appdata% as a shortcut because that should take you to the new Windows drive. Also if you are working your way down the path folder by folder you may not be able to see AppData, so try copying the entire folder path, substituting the right drive letter and username and pasting it in to File Explorer. In the folder called Profiles you should see at least one folder named xxxxxxx.default where the xxxx means a random string of 8 or more letters and numbers (and there could be more than one of those). The \Appdata\Roaming\Thunderbird path is the default for Windows installations. If your Profiles folder is not there, it may be that you chose to locate it somewhere else (mine is in F:\Programs\Mozilla), in which case I can't guess where it might be. Good luck hunting!

YAY!! I finally found it! One more question, please. To where do I copy the default files? I see on the current hard drive Windows-SSC (C:) > users <myname>, but there is no profile folder in there. Do I just copy to my user folder? I'm afraid to just give it a try in case it messes things up. Can I transfer the whole folder or just the contact and history info? Agnes, I truly appreciate your patience with my ignorance. Tom