Suggest: Reinstall Thunderbird. This is a common error after performing a windows system restore because this restores some mozilla files necessary for proper operations to a prior version, but not all of them! The Thunderbird program is not in the same place as your Thunderbird profile which contains emails. So, uninstalling and reinstalling should not effect emails. However, I would always advise making a backup if you do not have a recent one. '''How to create a backup info:''' * http://kb.mozillazine.org/Profile_backup '''How to uninstall:''' * Start > Control Panel > Programs and Features * select 'Mozilla Thunderbird' in list * click on uninstall '''How to install:''' Download Thunderbird for windows from this link - choosing the language version you prefer. * https://www.mozilla.org/en-US/thunderbird/all/ More helpful info on downloads: * https://support.mozilla.org/en-US/kb/installing-thunderbird-windows