Hi Do you have a backup/copy of your Profile from the old computer? If not, and if the files on the old hard drive cannot be recovered, you will probably not be able to restore the address book. If you can access a backup or copy of the Profile, you can copy all of the old content to your new installation. Or, assuming you have IMAP and have reconnected to the original emails from your account, you might rebuild it by opening emails from or to your contacts and adding them manually. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data