Go to Autodesk Motion FX's official website and get Autodesk Motion FXclear.exe. Open with the option administrator Run.
You need to begin your computer in safe mode. Then run the utility and identify the place of the Autodesk Motion FX program file in the next window or leave the default is correct. Then click Uninstall.
Wait for the process to complete. It may take some time. In the end, you need to restart your computer.