Click the search bar / white box near the sart menu and type %appdata%
Press enter
Delete the Mitel folder in the window that appears
Close this window
Click the search bar / white box near the sart menu and type c:\users\%USERPROFILE%\AppData
Press enter
Open the Local folder and delete the Mitel folder inside
Click the back button and browse to the the Roaming folder and delete the Mitel folder inside
Close all folders and relaunch Mitel Connect