FixMissingMSI.PowerShell - Windows Installer Cache Recovery Automation

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When Windows Installer cache files (C:\Windows\Installer\*.msi / *.msp) are missing, updates and uninstalls can fail for products like SQL Server, Exchange, Azure Arc Agent, and others.
The original FixMissingMSI utility identifies and restores these files but is GUI-only.

FixMissingMSI.PowerShell turns that manual process into a repeatable, non-interactive workflow.
It lets you scan systems at scale, merge reports, and repopulate missing files from a shared cache - all orchestrated through PowerShell.

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Features

• Non-interactive execution of FixMissingMSI via .NET Reflection
• Centralized reporting of missing MSI/MSP files
• Shared cache support with demand-driven population
• Secure ACL design for file share permissions
• Advanced recovery helpers for MSI registration scrubbing

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Installation

From the PowerShell Gallery:

Install-Module FixMissingMSI.PowerShell
Import-Module FixMissingMSI.PowerShell

Or from source:

git clone https://github.com/ITJoeSchmo/FixMissingMSI.PowerShell
Import-Module ./src/FixMissingMSI.PowerShell.psd1

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Exported Functions

Function	Purpose
Initialize-InstallerCacheFileShare	Prepare a file share with the tool and reports, apply scoped ACLs
Invoke-InstallerCacheRepair	Run FixMissingMSI non-interactively and output per-host CSV reports
Merge-InstallerCacheReports	Merge host reports into a deduplicated summary
Update-InstallerCache	Populate the shared cache with only the required MSI/MSP files

Update-InstallerCache copies only the specific MSI/MSP files that appear as missing in any server’s report -- it does not mirror every installer file from each system’s installer cache This keeps the cache lean and focused on real recovery needs.

Key Parameters: Invoke-InstallerCacheRepair

Parameter	Type	Description
FileSharePath	String (Required)	UNC path where the shared FixMissingMSI directory exists (e.g. \\FS01\Software ).
SourcePaths	String[]	One or more local or UNC paths containing MSI/MSP to scan as source for recovering missing files. By default, it also checks the shared cache (e.g. \\FS01\Software\FixMissingMSI\Cache\{Products, Patches}).
LocalWorkPath	String	Local directory where FixMissingMSI is staged and executed locally. Defaults to $env:TEMP\FixMissingMSI.
RunFromShare	Switch	Runs FixMissingMSI directly from the network share instead of copying locally.
ReportOnly	Switch	Performs discovery and reporting only -- no 'FixCommands' are executed, but still logs all FixCommands to the transcript and exports unresolved entries to CSV.. Useful for audit-only scans.

For full syntax, parameters, examples of other functions run:

Get-Help <function> -Full

Extra

Function	Purpose
Get-InstallerRegistration	Lists MSI-registered products from the Windows Installer registry.
Remove-InstallerRegistration	Forcefully removes or scrubs MSI registrations when standard uninstall or repair isn’t possible.

⚠️ Warning Remove-InstallerRegistration is an advanced recovery function adapted from Microsoft’s Program Install and Uninstall Troubleshooter (MSIMATSFN.ps1). It should be used only after standard uninstall or repair methods have failed.

When invoked, the function first attempts a normal uninstallation by calling msiexec /x <ProductCode> to remove program files and registry data through Windows Installer.

• After msiexec, the function runs the Rapid Product Removal (RPR) phase, which scrubs Windows Installer registration, cached metadata, and uninstall entries so that the product can be reinstalled.
• When run with -DeepClean, it additionally performs Microsoft’s LPR phase, which locates and purges related files, shims, ARP entries, and orphaned registry keys.

During either cleanup phase, the function automatically:

• Backs up files and registry data related to the target product under C:\MATS\<ProductCode>\
• Generates a PowerShell restore script (RestoreYourFilesAndRegistry.ps1) in the same directory, which can be used to revert any changes if needed.

These backups are created before any deletion occurs, allowing administrators to inspect or restore the removed data manually if necessary.

This command is intended strictly as a last-resort recovery tool to enable clean reinstallation of affected software. Always verify backups or create a system restore point before use.

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Quickstart

# Initialize cache share
Initialize-InstallerCacheFileShare -FileSharePath "\\FS01\InstallerCache"

# Scan a system and try to source missing files from "\\FS01\SQLServer2019\setup\"
Invoke-InstallerCacheRepair -FileSharePath "\\FS01\InstallerCache" -SourcePaths "\\FS01\SQLServer2019\setup\"

# Merge reports
Merge-InstallerCacheReports -FileSharePath "\\FS01\InstallerCache"

# Populate shared cache
Update-InstallerCache -FileSharePath "\\FS01\InstallerCache"

Full example workflows are provided under examples/.

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Common Errors

This project automates recovery for:

• The cached MSI file 'C:\Windows\Installer\xxxxxx.msi' is missing
• SQL Server Setup has encountered the following error: The cached MSI file is missing
• Missing MSI/MSP files prevent service pack or cumulative update installation

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Security Posture

• The application folder is read/execute only for Domain Computers
• Cache and reports folders are writable as scoped
• Servers cannot write to the tool folder itself

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How the Non-Interactive Execution Works

FixMissingMSI is a WinForms GUI with no CLI support. This module loads the EXE via .NET Reflection, instantiates its form classes to initialize internal state, and invokes internal methods directly.

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Credits

• FixMissingMSI authored by suyouquan (Simon Su @ Microsoft)
• Installer-registration helper functions adapted from Microsoft’s Program Install and Uninstall Troubleshooter

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Roadmap

• Add orchestration examples for Ansible and Azure Arc
• Evaluate replacing FixMissingMSI dependency with native implementation (Update-InstallerCache already functions independently)

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License

MIT License © 2025 Joey Eckelbarger