Start the Windows Installer Service manually by using the control panel, by activating the service via a command prompt, or by uninstalling previous versions of the software. Microsoft designed the Windows Installer Service to run automatically when a computer user attempts to install new software.
Apps designed to run on the Windows 10 operating system do not use this service, but users may still have legacy software applications that require this service. When installing such software, a user may encounter an error message stating “The Windows Installer service could not be accessed.” In this event, the user can manually start the service by accessing the Services tab under the Control Panel, or manually, by typing “net start MSIServer” in the command prompt and restarting the installation process for the program he wishes to install. Microsoft also has a registry fix for this problem on the support section of its website.