Replacing such hardware shouldn't remove any data. * Is the address book the only data missing? * Did you have to reinstall any software or move any files? * Did you [https://support.mozilla.org/en-US/kb/profiles-tb#w_backing-up-a-profile make a backup of your Thunderbird profile in the recent past]? Your Thunderbird data is stored in [https://support.mozilla.org/en-US/kb/profiles-tb a profile folder]. [http://kb.mozillazine.org/Moving_address_books_between_profiles This article provides detailed information about addressbooks files]. * Are the files still there? Having the information requested above will also help, thanks in advance.