Table of Contents
- Is it safe to uninstall Windows 11 KB5074109 to fix Outlook and OneDrive crashes?
- Critical Advisory: Windows 11 KB5074109 Stability Analysis
- The Core Conflict: Outlook Classic and OneDrive
- The Technical Failure Mechanism
- Microsoft’s Official Recommendation
- Broader System Regressions
- Sleep Mode (S3) Failure on Legacy Hardware
- Desktop and Visual Resets
- File Explorer Customization Breaks
- Third-Party App Unresponsiveness
- Strategic Mitigation: How to Uninstall KB5074109
- Post-Removal Advisory
Is it safe to uninstall Windows 11 KB5074109 to fix Outlook and OneDrive crashes?
Critical Advisory: Windows 11 KB5074109 Stability Analysis
The mandatory January 2026 update for Windows 11, identified as KB5074109, introduces severe stability regressions. These defects primarily affect professional workflows relying on Outlook Classic, POP email protocols, and OneDrive synchronization.
If your system runs OS Build 26200.7623 or 26100.7623, this update is installed. Users prioritizing operational stability over the latest security patches may need to roll back this update immediately.
The Core Conflict: Outlook Classic and OneDrive
Microsoft confirms a critical conflict between the OneDrive sync engine and Outlook Classic data files. This issue specifically impacts users who store Personal Storage Table (PST) files within folders synced to OneDrive.
The Technical Failure Mechanism
When Outlook Classic utilizes a POP account, it writes data locally to a PST file. Under normal operation, Outlook updates this file upon closing to save “Sent Items” and index data. With KB5074109 installed, OneDrive aggressively locks the PST file for scanning or uploading during this process.
Because OneDrive holds the file handle, Outlook cannot complete its write operation. This results in:
- Process Hangs: The application interface closes, but Outlook.exe remains active and frozen in the background.
- Data Inconsistency: Emails sent during the session fail to appear in the “Sent Items” folder.
- Launch Failures: Subsequent attempts to open Outlook fail because the previous instance never terminated.
Microsoft’s Official Recommendation
Microsoft support documentation currently advises users to access email via web browsers (Webmail) until a patch is deployed. The alternative—moving PST files out of OneDrive directories—is technically complex and risks data fragmentation.
Broader System Regressions
Beyond email functionality, KB5074109 disrupts several legacy and customization features essential for power users and enterprise environments.
Sleep Mode (S3) Failure on Legacy Hardware
Older hardware configurations utilizing the S3 power state (Suspend-to-RAM) may lose sleep functionality. Modern systems utilizing S0 Low Power Idle remain unaffected. To verify your power state capability, execute powercfg /a in the Command Prompt.
Desktop and Visual Resets
The update triggers intermittent black screens upon login. It may also forcefully reset desktop wallpaper customizations to a blank black background, requiring manual restoration via Personalization settings.
File Explorer Customization Breaks
Enterprise environments often use desktop.ini files to mask raw folder paths with user-friendly names (LocalizedResourceName). KB5074109 breaks this parsing logic. File Explorer now ignores these display instructions, revealing the raw underlying directory names despite correct attribute settings.
Third-Party App Unresponsiveness
Applications beyond Outlook that rely on cloud-synced storage (Dropbox, OneDrive) face similar file-locking issues. Users report inability to save or open files directly from these locations.
Strategic Mitigation: How to Uninstall KB5074109
If these defects impede your daily operations, removing the update restores functionality. Note that this action removes over 100 security patches included in the January release. Proceed only if workflow continuity outweighs immediate security risks.
Step-by-Step Removal Process
- Navigate to Settings > Windows Update.
- Select Update history.
- Scroll to the bottom and click Uninstall updates.
- Locate Security Update for Microsoft Windows (KB5074109).
- Click Uninstall and confirm the prompt.
- Allow the system to restart.
Post-Removal Advisory
Once the system reboots, Outlook Classic will function correctly. You must immediately pause Windows Updates in Settings for 1-2 weeks. Failing to pause updates will cause Windows to automatically reinstall the defective patch overnight. Microsoft is currently developing a resolution for a future release.