How do I fix the Windows Installer service could not be accessed?

Start the service with "net start msiserver" from an elevated terminal. If that fails, set Windows Installer to Manual in services.msc, then re-register it with "msiexec /unregister" followed by "msiexec /regserver".

The Windows service that installs, repairs and removes MSI packages. It starts on demand rather than running constantly, which is why a broken or disabled msiserver only shows up the moment you try to install something.

Is error 1719 caused by the program I am installing?

Almost never. It is a system-level failure, so it hits every MSI package equally. If other installers work, look at that specific program instead.

Installation errors

Error 1719

The Windows Installer Service could not be accessed. This can occur if the Windows Installer is not correctly installed.

The service that installs every MSI package on Windows is not running, or its registration is damaged. Nothing installs until it is fixed, and the fix is usually two commands.

What it actually means

Every .msi on Windows is handled by a system service called msiserver. It is set to start on demand, so you never notice it until it fails to start. When it cannot be reached, every MSI installation and uninstallation fails with 1719 regardless of which program you were installing, which is the clue that this is not the program’s fault.

How to fix it, in order

Ordered by how often each one is the answer, not by how clever it sounds.

01Start the service by hand: open an elevated terminal and run "net start msiserver". If it starts, retry the installation immediately.
02Check it is not disabled. Run services.msc, find Windows Installer, and set the startup type to Manual. Disabled is a common leftover from "optimisation" tools.
03Re-register the service: run "msiexec /unregister" and then "msiexec /regserver" from an elevated terminal. This rebuilds the registration without touching your installed programs.
04Repair system files if the service still will not start: "sfc /scannow" followed by "DISM /Online /Cleanup-Image /RestoreHealth". The service is part of Windows, so damage to it is damage to the system.
05Check that the SYSTEM account still has full control over HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer. Permission changes here break the service in exactly this way and are hard to spot otherwise.

If it happens with every installer, it is not the installer

The useful diagnostic is breadth. A program that fails while others install fine has its own problem. When nothing MSI-based will install or uninstall, the service is the common factor and there is no point re-downloading anything.

Uninstalling from the command line, which needs the same service

Common questions

How do I fix the Windows Installer service could not be accessed?: Start the service with "net start msiserver" from an elevated terminal. If that fails, set Windows Installer to Manual in services.msc, then re-register it with "msiexec /unregister" followed by "msiexec /regserver".
What is msiserver?: The Windows service that installs, repairs and removes MSI packages. It starts on demand rather than running constantly, which is why a broken or disabled msiserver only shows up the moment you try to install something.
Is error 1719 caused by the program I am installing?: Almost never. It is a system-level failure, so it hits every MSI package equally. If other installers work, look at that specific program instead.

Before you retry the installer

If the package came from anywhere other than the publisher, confirm it is the file they actually shipped. Check its SHA-256 against our index, which settles in seconds whether you are debugging an installer or a damaged download.