Thunderbird is a free, open-source email client provided by Mozilla, makers of the Firefox browser. Much like Firefox, Thunderbird allows for the installation of third-party add-ons that can extend the functionality of the email client. Uninstalling the application is simple, though it will leave behind a folder of all your Thunderbird data. To completely remove the application, you must delete this stored data. Once removed, reinstalling the application is just a matter of redownloading the installer file from Mozilla.
Select "Control Panel" from the Start menu, select "Programs and Features," then "Programs."
Select Mozilla Thunderbird from the list of installed applications, click "Uninstall" to remove the application. Confirm the action.
Open the Start menu, type "folder options" into the Search menu to bring up the Folder Options control panel. Select "View" and enable "Show hidden files and folders." Click "Apply," then "OK" to save the changes.
Open the Start menu, type "%APPDATA%" into the Search box, select "Roaming" from the returned listed.
Select "Thunderbird," then "Profiles" in the Windows Explorer window that opens.
Select all profile folders, right-click them and select "Delete."
Right-click the Recycle Bin on your desktop, select "Empty Recycle Bin." This permanently deletes all your stored Thunderbird data (messages, preferences, add-ons).
Open a Web browser and navigate to Mozilla's Thunderbird site (see Resources). Click "Download" and save the Thunderbird installer to your desktop.
Double-click the downloaded installer to begin reinstalling the application.