Microsoft has acknowledged a Windows 11 known issue that’s leaving some Samsung computers unable to access their main storage drive after installing recent updates. The problem has been linked to the February 2026 security update KB5077181 (and any later updates), and it can cause a serious error message on affected machines: “C: is not accessible – Access denied.” When that happens, users may be blocked from opening files, launching certain apps, or completing common system tasks that rely on access to the C: drive.
The issue appears to be limited to specific Samsung devices running Windows 11 24H2 and Windows 11 25H2. Microsoft says it has observed the behavior on some Samsung Galaxy Book 4 models and certain Samsung desktop systems. The affected model list includes NP750XGJ, NP750XGL, NP754XGJ, NP754XFG, NP754XGK, DM500SGA, DM500TDA, DM500TGA, and DM501SGA.
What makes this situation especially confusing for users is how it shows up during everyday use. Microsoft notes that people can run into the error simply by opening files, launching applications, or attempting administrative actions. In more severe cases, permission failures can prevent users from elevating privileges, uninstalling updates, or collecting diagnostic logs—steps that many people would normally try when troubleshooting.
While the reports surfaced around the same time as Patch Tuesday updates, Microsoft says its investigation with Samsung points to a different root cause. According to the companies, the Windows updates themselves are not the underlying reason for the C: drive access failure. Instead, the symptoms were traced to a problem in the Samsung Galaxy Connect app. In other words, the issue is associated with systems that installed KB5077181 and later updates, but Microsoft is attributing the actual trigger to Samsung software rather than the Windows 11 cumulative update package.
Microsoft also says mitigation steps are already in place to reduce the chance of more devices being affected. As part of that effort, the problematic version of Samsung Galaxy Connect was temporarily removed from the Microsoft Store to prevent new installs. Samsung has also republished a stable earlier version of the app, which should help stop the issue from recurring on additional PCs.
For people whose computers have already been impacted, the path to recovery may still be limited for now. Microsoft says Samsung is evaluating remediation options with Microsoft’s support, and affected users are currently being advised to contact Samsung’s support channels for model-specific guidance.
Microsoft’s incident entry notes the issue was opened on March 13, 2026, and last updated on March 14, 2026. If you’re using one of the listed Samsung models on Windows 11 24H2 or 25H2 and suddenly can’t access the C: drive, this known issue—and the Samsung Galaxy Connect app—may be the reason.
