Symptoms

When installing or uninstalling the program, the following error occurs: 

’The Windows Installer Service could not be accessed. This can occur if you are running Windows in safe mode, or if the Windows Installer is not correctly installed. Contact your support personnel for assistance.’

  

Cause

The Windows Installer Service that is included with OS is unregistered or damaged.

 

Resolution

Follow the steps in the following Microsoft Knowledge Base article: 
https://answers.microsoft.com/en-us/windows/forum/all/windows-installer-service-could-not-be-accessed/8e9cd803-14dd-493b-8e8a-588767ca1530