Try this: Exit Thunderbird. Uninstall Thunderbird. Download a fresh version and install. Thunderbird program and Thunderbird Profile folders are not the same thing and not stored in same place. So you should be able to uninstall Thunderbird and then reinstall a fresh version without any effect on emails etc. However, it is always a good idea to create a backup periodically, so perhaps now would be a good time to do it. Info on creating a backup: * http://kb.mozillazine.org/Profile_backup * http://kb.mozillazine.org/Profile_folder_-_Thunderbird * https://support.mozilla.org/en-US/kb/profiles-tb To uninstall: Start > Settings >Control Panel > 'Programs and Features' select 'Mozilla thunderbird' and click on uninstall. To install, download from either of these links: https://www.mozilla.org/en-GB/thunderbird/ OR this page shows a load of different languages and OS options: https://www.mozilla.org/en-US/thunderbird/all/