Major Windows 11 Bug Renders C: Drive Inaccessible, Severely Impacting Specific Devices

Microsoft has officially acknowledged a significant flaw within Windows 11, where a recent update is causing the system’s primary C: drive to become inaccessible for certain users. This critical issue stems from the February 2026 Patch Tuesday update, identified as KB5077181, leading to an alarming ‘C:\ is not accessible – Access denied’ error.

Widespread Disruption from the Latest Patch

The implications of this bug extend far beyond a simple inability to browse the C: drive in File Explorer. Users are reporting that numerous essential applications, including email clients like Outlook, popular web browsers, and various system utilities, are failing to launch. This effectively cripples the affected computers, preventing common actions such as accessing files, executing routine tasks, and even elevating user privileges for administrative functions, severely hindering daily productivity.

Targeted Impact and Ongoing Investigation

While the bug is severe, it is important to note that it does not affect all Windows 11 installations. Microsoft’s documentation indicates that the problem is ‘predominantly observed’ on specific Samsung laptop models, particularly the Samsung Galaxy Book4, in regions including Brazil, Portugal, Korea, and India. Initial investigations suggest the Samsung Share application might be connected to the root cause, though Microsoft is still actively working to fully validate this hypothesis.

The issue specifically targets Windows 11 versions 24H2 and 25H2. Users operating on Windows 10 or earlier Windows 11 builds (23H2 and older) are not expected to encounter this particular problem.

Temporary Solutions and Official Guidance

In the absence of an immediate official patch, some frustrated users on platforms like Reddit have reported success with a risky workaround involving changing the ownership of the C: drive and its contents. However, this method carries inherent risks and is generally not recommended for the average user unless absolutely necessary.

For most affected users, Microsoft’s primary advice is to await an official fix. While rolling back the problematic update might be an option, if it doesn’t resolve the issue, patience is advised. Notably, Microsoft subsequently published an official workaround for affected systems on March 16, 2026.