I cannot run .msi files.

Question

I got a virus on my laptop and it messed up some files. After i clean up the lap i can't run msi files. When i tried to run a file it says you'll need a new app to open this msi file. Its like when you don't have a default video player and try to open a video and it asks you to choose a player to open it. I tried fix it withr registry editor but msi services file is completely missing. Can i fix this without reinstalling windows? How can i fix it?

Answer 1

1

On the link below, scroll down to find MSI in the long table that lists all file types..

https://www.elevenforum.com/t/reset-and-restore-default-apps-for-file-types-in-windows-11.2139/

Click MSI to download the registry file.

Right click the registry file you downloaded and select 'Merge', then confirm the merge.

Restart (not shut down) your PC to apply the change and set the file associations on MSI files, then try opening an MSI installer.

2

If that does not resolve the problem.

Open Command Prompt by right clicking its icon and select 'Run as Administrator.

Run this command and press Enter.

msiexec /unregister

Run this command and press Enter.

msiexec /regserver

Close Command Prompt, then try opening an MSI installer.

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Answer 2

The described behavior (file types opening with the wrong handler or prompting for an app) matches a damaged file-association/registry state after malware infection. This can be repaired without reinstalling Windows by restoring the affected associations and then repairing Windows Installer.

Follow these steps in order:

1. Repair general executable/file associations
   • The malware likely corrupted multiple associations (.exe, .com, .bat, .cmd, .reg, etc.), not just .msi.
   • Use Registry Editor to remove the per-user overrides so Windows can fall back to the correct system defaults:
     1. Open Regedit:
        • Press Start → Run, type explorer, press OK.
        • Go to the Windows folder (for example, C:\Windows) and locate regedit.exe.
        • On Windows 7 or Vista: right‑click regedit.exe → Run as administrator and accept the UAC prompt.
     2. In Registry Editor, browse to: HKEY_CURRENT_USER\Software\Classes
     3. In the left pane, right‑click and Delete each of these subkeys if present:
        • .exe
        • .com
        • .bat
        • .cmd
        • .reg
        • .regedit
        • secfile
     4. Close Registry Editor.
   • This removes user-level overrides that malware commonly uses so that system defaults can work again.
2. Scan again for malware
   • After fixing the registry, run an updated antivirus scan to ensure no active malware is still modifying associations.
   • If no antivirus is installed, use the free Microsoft Safety Scanner from Microsoft to clean remaining malware.
3. Repair Windows Installer and MSI handling
   • If MSI packages still do not run, repair Windows Installer configuration:
     1. Run the Fix problems that programs cannot be installed or uninstalled troubleshooter to repair registry keys that block MSI-based installs.
     2. If MSI-based installs still fail or show installer errors, obtain a fresh copy of the MSI package:
        • Download the latest version of the installer from the software vendor.
        • Save it locally (for example, to C:\Temp) and run it from there instead of from a network share or old media.
     3. If the MSI file is part of an application already installed and repair operations are failing, use Windows Installer’s repair mechanisms (from Programs and Features) so that missing components and files are reinstalled.
4. If MSI repair operations show UAC prompts or fail
   • In managed environments where MSI repair is blocked or repeatedly prompts for elevation, administrators can configure Windows Installer policies (for example, allowlists for secure repair) via the registry under: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\Installer
   • This is typically done by IT admins and not required on home systems, but is relevant in System Center–managed environments.

If, after these steps, MSI files still prompt for “you’ll need a new app to open this .msi file,” the system is likely more extensively damaged and an in-place upgrade/repair install of Windows may be required, but that is beyond the information provided in the context.

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References:

• When you open a file on a Windows based computer, the file may start a different program
• How to troubleshoot Windows Installer errors
• Installing a Missing Component
• I (Windows Installer)
• Unexpected UAC prompts when running MSI repair operations after installing the August 2025 Windows security update