Copy and paste %appdata%\Sidekickinto yourStartmenu in Windows and press Enter.
Remove all contents in the folder.
Start up Outlook.
Please note: if you encounter an error message that the folder or file(s) are currently in use when you attempt to delete them, close all instances of Outlook and Sidekick for Windows. Press Ctrl + Alt + Delete and click Task Manager. Ensure you are in the Processes tab, then locate and right-click the SidekickTrayWPF process and click End Task. Then, attempt to delete the folder or file(s) again.