What causes Error 1445?

User account lacks required permissions. Group Policy restricts access. Authentication credentials expired. UAC is blocking the action

How do I fix Error 1445 (ERROR_NON_MDICHILD_WINDOW)?

Run as Administrator: Right-click the application → 'Run as administrator'. If Error 1445 (ERROR_NON_MDICHILD_WINDOW) resolves, it's a permissions issue. For permanent fix, right-click → Properties → Compatibility → check 'Run as administrator'

Fix ERROR_NON_MDICHILD_WINDOW — Windows Error Code 1445

Q: What is Windows Error 1445 (ERROR_NON_MDICHILD_WINDOW)?

Error 1445 (ERROR_NON_MDICHILD_WINDOW) is a Windows Security & Privileges error that occurs when cannot process a message from a window that is not a multiple document interface (mdi) window.. This guide provides step-by-step solutions to resolve this issue.

🎮 Common Scenario: Are you experiencing Error 1445 while launching or installing Valorant? The solutions below directly address the system interactions specific to this application.

⚡ Quick Fix

Run as Administrator: Right-click the application → 'Run as administrator'

👇 See all 2 solutions below

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📑 Table of Contents

What is Error 1445? Common Causes Step-by-Step Solutions Prevention Tips Related Errors

💡 What is Error 1445?

Windows System Error Code 1445, known as ERROR_NON_MDICHILD_WINDOW, is a Security & Privileges error that occurs during security, authentication, and user privileges. The error indicates that: Cannot process a message from a window that is not a multiple document interface (MDI) window. When this error is encountered, the Windows operating system was unable to complete the requested operation within the security services subsystem. The error code 1445 is returned by the GetLastError() function and provides developers with a specific identifier to diagnose the root cause of the failure. The symbolic name ERROR_NON_MDICHILD_WINDOW maps directly to this numeric code and is commonly referenced in Microsoft documentation, developer forums, and system logs. Understanding this error and its context within security, authentication, and user privileges is essential for effective troubleshooting.

⚠️ Common Causes

User account lacks required permissions
Group Policy restricts access
Authentication credentials expired
UAC is blocking the action

✅ Step-by-Step Solutions

1 Run as Administrator

Right-click the application → 'Run as administrator'
If Error 1445 (ERROR_NON_MDICHILD_WINDOW) resolves, it's a permissions issue
For permanent fix, right-click → Properties → Compatibility → check 'Run as administrator'

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Show Advanced Solutions (1 more)

2 Check User Account Permissions

Open Computer Management (compmgmt.msc)
Navigate to Local Users and Groups → Users
Verify your account is in the Administrators group
If not, add it and log off/on

🎬 Video Tutorials

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💻 Diagnostic Command

Run this PowerShell command to find related events in your system log:

Get-EventLog -LogName System -Newest 20 | Where-Object {$_.Message -like "*1445*" -or $_.Message -like "*ERROR_NON_MDICHILD_WINDOW*"} | Format-List

💡 Open PowerShell as Administrator, paste the command above, and press Enter.

🛡️ Prevention Tips

Apply least-privilege principle
Audit user accounts regularly
Keep security policies and AV updated

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Last updated: 2026-03-13

📖

Based on Official Microsoft Documentation

Solutions Tested on Windows 10 & 11

Error codes sourced from Microsoft Win32 SDK. Updated 2026-03-13.