Thunderbird includes a Software Update feature that automatically checks for updates and prompts you to install them when necessary. For more information about the Software Update feature, see Update Thunderbird to the latest version.

Sometimes, the updater fails and displays the following error message:

This article presents possible solutions to this problem and workarounds to get Thunderbird updated.

Another user is running Thunderbird

If you share your computer with other users, and another user's account is still logged in with Thunderbird running, this error can occur. Make sure you're the only user logged in to the computer when updating Thunderbird. The easiest way to do this is to restart your computer. Once the computer starts up again, start Thunderbird, click the Help menu, and select Check for Updates....

End all Thunderbird processes and restart Thunderbird

End any Thunderbird processes that may still be active, either manually or by restarting your computer.

Once all instances of Thunderbird have been ended or after the computer starts up again, restart Thunderbird to see if the updater is now working.

Ending Thunderbird processes on Windows

You can manually end the Thunderbird process using Windows Task Manager.

1. Right-click on an empty spot in the Windows task bar and select Task Manager (or press Ctrl+Shift+Esc).
2. Select the Processes tab.
3. Select the thunderbird.exe entry in the processes list, click End Process and click Yes in the "Task Manager Warning" dialog that appears.

Run Update as Administrator

If you are using Windows 7 or Vista:

1. End the Thunderbird process in Windows Task Manager as explained above, or reboot the computer so that no Thunderbird processes are active.
2. Open the Windows Start Menu, type thunderbird and right-click on the "Mozilla Thunderbird" entry that appears.
3. Select Run as Administrator and Continue if the User Account Control dialog comes up.

If the issue is not resolved, end Thunderbird again, as explained above, but this time, open the C:\Program Files\Mozilla Thunderbird folder, right-click on the thunderbird or thunderbird.exe file icon and select Run as Administrator.

Did you edit msconfig or stop Application Experience?

If the issue is not resolved, you may have stopped the service "Application Experience" or disabled "Application Experience" in msconfig.

1. Right-click on an empty spot in the Windows task bar and select Task Manager (or press Ctrl+Shift+Esc).
2. Select the Services tab. Start the service "AeLookupSvc - Application Experience". If you are unable to start it, you may have disabled "Application Experience" in msconfig.
3. To edit msconfig, press the Windows button and type "msconfig" and select the program that is displayed. Select the Services tab. Make sure that "Application Experience" is enabled. Click OK and restart your computer if needed.

Last resort

If you have tried every solution above and you still see the Software Update Failed message, you can update Thunderbird by installing the new version over top of your current version.

Based on information from Software Update (mozillaZine KB)