Error: “An existing installation of the Act! Web API has been detected. Please uninstall the Act! Web API before installing this version of Act!” when attempting to install Act! Premium v20 (access via web)

Symptom: When I try to install Act! Premium v20 (access via web), I receive the Error: “An existing installation of the Act! Web API has been detected. Please uninstall the Act! Web API before installing this version of Act!"

Product Details:
Product Family: Act!
Product: Act! Premium (access via web)
Version: v20

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Cause:
This can occur if you installed the Act! Premium Web API for a previous version of Act! on this machine, and did not uninstall it before attempting to install Act! v20, which automatically installs the current version of the Act! Premium Web API.

Solution:

Note: Before proceeding with these steps, it will be necessary to make sure that your system is configured to display hidden files and folders. For information regarding this configuration, refer to the following knowledgebase article:

How to configure Windows to show hidden files and folders and/or show file extensions for known file types

1. Uninstall the previous version of the Act! Premium Web API by following the steps in the following knowledgebase article:
   
   How do I uninstall the Act! Premium Web API?
   
   
   
2. Navigate to C:\Program Files (x86)\InstallShield Installation Information
3. Look for one or both of the following folders:
   
   • {5D1AA87E-D986-421F-883B-CC226D834925}
   • {BFF41704-DBD7-4016-B19C-7F314DEB0C0B}
   
   
4. If these folders exist, rename them by adding OLD to the end of the folder name
5. Attempt to install Act! v20 again to test