Microsoft has officially acknowledged a significant bug within Windows 11 that is severely impeding the functionality of certain PCs. The issue, which emerged after the February 2026 Patch Tuesday update (KB5077181), prevents users from accessing their primary system drive, often designated as C:.
This widespread problem is more than just an inconvenience; it effectively cripples affected computers, making essential operations impossible and displaying a persistent ‘C:\ is not accessible – Access denied’ error message.
The Pervasive Impact on System Functionality
The ramifications of this Windows 11 bug extend far beyond merely opening File Explorer. According to Microsoft’s updated documentation, the inability to access the C: drive directly translates into popular applications failing to launch. This includes crucial software such as Microsoft Outlook, various Office suite components, web browsers, and even standard system utilities. Tasks that require elevated privileges, file access, or common daily operations become non-functional.
Users report being unable to perform routine administrative duties, uninstall updates, or even gather diagnostic logs, creating a highly frustrating and debilitating user experience.
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Targeted Devices and Ongoing Investigation
While the bug’s description is alarming, Microsoft confirms that not all Windows 11 systems are vulnerable. The issue is predominantly observed on specific Samsung laptop models, particularly the Samsung Galaxy Book4 and other consumer devices, across various international regions including Brazil, Portugal, Korea, and India.
Initial investigations suggest that the ‘Samsung Share’ application could be a contributing factor, though this root cause is still undergoing full validation by Microsoft. Importantly, this bug affects only Windows 11 versions 24H2 and 25H2. Users running Windows 10 or older Windows 11 versions (23H2 and earlier) appear to be unaffected by this particular problem.
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For those impacted, extreme caution is advised regarding community-suggested workarounds, such as manually changing ownership of the C: drive. While some users on platforms like Reddit claim this offers a temporary fix, Microsoft has not endorsed such methods, deeming them potentially risky. The official recommendation for most users, especially if rolling back the problematic update proves ineffective, is to await a formal resolution from Microsoft.
Microsoft’s Response and Future Fixes
Microsoft has acknowledged the severity of the situation and is actively investigating the bug to identify a definitive fix. An official workaround was subsequently published on March 16, 2026, offering guidance to affected users. Device owners experiencing these critical issues should monitor official Microsoft channels for further updates and solutions.
