When updating the Veeam Agent for Microsoft Windows deployment on a machine that is part of a 'Computers with pre-installed agents' Protection Group, attempting to run VeeamInstallerSvc.msi causes the error message:
Another version of this product is already installed. Installation of this version cannot continue. To configure or remove the existing version of this product, use Add/Remove Programs on the Control Panel.
This error occurs because the existing version of the Veeam Installer Service must be uninstalled before installing a new version.
Review the Update Procedure for Windows Computers section of the Veeam Agent Managed User Guide for more information on updating Windows computers associated with a 'Computers with pre-installed agents' Protection Group.