Parallels Toolbox for Windows needs reinstallation

Symptoms

• I got a pop-up message upon Parallels Toolbox start that the application needs to be reinstalled:

  "Windows has been updated. Please reinstall Parallels Toolbox to ensure that it functions correctly."

Cause

Windows registry was affected after updating Windows to new build. In particular, the following registry key is missing in Windows registry:

    HKEY_LOCAL_MACHINE\SOFTWARE\Parallels\Parallels Toolbox

Resolution

1. Download the Parallels Toolbox installation file.
2. Reinstall Parallels Toolbox.