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How to fix Error 1603: A fatal error occurred during installation

Error code: INSTALLER-ERROR-1603

What this error means

A Windows Installer (.msi) setup stops with "Error 1603: A fatal error occurred during installation" and rolls back. Microsoft lists four causes: the app is already installed, the target folder is encrypted, the target drive is a substituted drive, or the SYSTEM account does not have Full Control of the folder (Windows Installer installs software as SYSTEM). The code itself is generic, so if none of these apply, an installation log shows the step that actually failed.

Updated

Applies to
Windows 11 and Windows 10, programs installed with Windows Installer (.msi)
Difficulty
Beginner to intermediate
Before changes
Low; permission changes on a drive take effect for all its folders

Reviewed by Matyáš Rada · Documentation checked: 2026-10-31 · Checked against Microsoft's MSI error 1603 article and msiexec documentation; not tested with every installer.

Before you begin

Note which program you are installing and the folder it installs to. Restart the PC once before trying again, in case another installation is still running. If Windows cannot start, see the startup guide.

Work through these checks

0 of 7 complete
01Uninstall any existing copy

Microsoft's first cause is that Windows Installer is trying to install an app that is already installed.

  1. Open Settings > Apps > Installed apps and search for the program, including older versions.
  2. Uninstall it, restart the PC and run the installer again.
What to expect

The installation completes.

If it does not help

If the old version cannot be uninstalled, use the maker's cleanup tool in step 7.

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02Install to a folder that is not encrypted

Microsoft lists an encrypted target folder as a cause.

  1. Right-click the target folder > Properties > Advanced and check whether Encrypt contents to secure data is ticked.
  2. If it is, choose a different, unencrypted folder in the installer, for example the default folder under C:\Program Files.
What to expect

The installation completes in the unencrypted folder.

If it does not help

BitLocker drive encryption is different and does not cause this error.

Browse related errors
03Avoid substituted drives

Microsoft lists installing to a drive accessed as a substitute drive as a cause.

  1. In Command Prompt, run subst to list substituted drives.
  2. If the target drive letter appears in the list, install to the real drive and folder instead.
What to expect

The installer targets a normal drive.

If it does not help

Mapped network drives can cause similar problems; install to a local drive.

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04Give SYSTEM Full Control of the target drive

Windows Installer uses the SYSTEM account, and Microsoft lists missing Full Control as a cause.

  1. In File Explorer, right-click the target drive > Properties > Security.
  2. Check that SYSTEM is listed. If not, click Edit > Add, type SYSTEM, click Check Names and OK.
  3. Click Edit, select SYSTEM and make sure Full control is set to Allow.
  4. Click Advanced > Change permissions, select SYSTEM > Edit, set Applies to: This folder, subfolders and files, click OK and let Windows apply the permissions. Then run the installer again.

Do not remove other entries such as Administrators or Users while you are on this tab.

What to expect

SYSTEM has Full control and the installation completes.

If it does not help

Applying permissions to a large drive can take several minutes.

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05Check the Windows Installer service

If the Windows Installer service cannot start, MSI installations fail.

  1. Press Win + R, type services.msc and find Windows Installer.
  2. Its Startup type should be Manual, not Disabled. If it is Disabled, set it to Manual and click Apply.
What to expect

The service is not disabled and can start when an installer runs.

If it does not help

If the service will not start at all, run DISM /Online /Cleanup-Image /RestoreHealth and sfc /scannow in Terminal (Admin).

Browse related errors
06Create an installation log

Error 1603 is a general failure; a verbose log shows the actual step that failed.

  1. Open Command Prompt (Admin) in the folder with the .msi file.
  2. Run msiexec /i "package.msi" /l*v "%temp%\install.log" (use the real file name).
  3. Open the log in Notepad and search for "Return value 3"; the lines just above it show what failed.

If the installer is an .exe, check the maker's documentation for its logging option.

What to expect

You find the action or file that caused the failure, such as a file in use, a missing prerequisite or an access error.

If it does not help

Search the program maker's support pages for that action name or message.

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07Use the maker's cleanup or repair tool

Many software makers publish tools that remove broken installations and leftovers that block a new install.

  1. Check the program maker's support site for an uninstall, cleanup or repair tool for that product, and run it.
  2. For Microsoft products, use the product's own repair option in Settings > Apps > Installed apps > Modify, if available.
  3. Restart and run the installer again.

Use cleanup tools only from the program's official maker.

What to expect

The installation completes on a clean system.

If it does not help

If the error remains, contact the program maker's support and include the log from step 6.

Browse related errors

Possible causes

  • The app, or an older version of it, is already installed
  • The target folder is encrypted
  • The target drive is a substituted (subst) drive
  • The SYSTEM account lacks Full Control on the target drive or folder
  • A product-specific step in the installer fails

Useful Windows tools

These commands open Windows tools. Review changes before applying them.

services.msc

Sources & further reading