Canon EOS-1D X Manual (en)

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Deleting the Software (Uninstalling)
Exit any applications before uninstalling the software.
Log in under an administrator-level privilege when uninstalling the 
software.
Uninstall the software according to the OS software uninstalling 
method.
To prevent computer malfunctions, always restart your computer after 
you have uninstalled the software. Re-installing the software without 
first restarting your computer is particularly likely to result in computer 
malfunctions.