Failure to install .Net agent

Document ID : KB000111080
Last Modified Date : 15/08/2018
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When installing .Net Agent , we get a popup box. It states -- "Version 8.0 or later of this product is already installed. Installation of this version cannot continue. To remove the existing version of this product, use Add/Remove Programs on the Control Panel." What should we do to resolve this and install the .Net agent?
All APM releases. 
Delete these keys from the Windows Server registry using Regedit
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\ComputerAssociates\Introscope\NETAgent (64bits machine)

The install should then be able to proceed.