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Summary
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The Windows 11 February Update (KB5077181) locks some Samsung PCs out of C: with a “C:\ is not accessible” error.
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Microsoft confirms that the Galaxy Book 4 and other Samsung models are affected; Samsung Share app is suspected but not confirmed.
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Some suggest changing C: permissions, but fixes are risky: uninstall the update or wait for a patch from Microsoft if you want to play it safe.
Windows 11 has had a terrible time with updates recently. In January, it seemed like not a week went by without something going wrong. While February seemed a bit quiet, it seems like the trend of strange bugs in Windows 11 continued into March. Microsoft has confirmed that some Samsung devices are receiving the “C:\ is not accessible – Access is denied” error after installing the latest Windows 11 updates.
Some Samsung devices can’t find their C: drives after Windows 11 February update
There are some solutions suggested by users, but they can be risky.
How he saw it neowinMicrosoft has updated its “Known issues and notifications for Windows 11, version 25H2“. This is where Microsoft posts new information about bugs and critical issues to keep everyone up to date on what the company is working on.
Recently, Microsoft added the following text to the March 2026 issues section:
Microsoft has received reports of an issue where some Samsung device models lose access to the C: drive after installing the February 2026 security update (KB5077181) and subsequent updates. Users may encounter the error “C:\ is not accessible – Access Denied”, which prevents access to files and blocks the launch of some applications, including Outlook, Office applications, web browsers, system utilities, and Quick Assist.
Affected devices encounter the issue when users perform common actions, such as accessing files, launching applications, or performing administrative tasks, and do not require any specific user action beyond routine operations. In some cases, users are also unable to elevate privileges, uninstall updates, or collect logs due to permission failures.
Microsoft notes that the issue appears to be an international issue affecting “(the) Samsung Galaxy Book 4 and other Samsung consumer devices.” Microsoft suspects it has something to do with Samsung Share, but isn’t sure yet.
Meanwhile, people flock to a Reddit thread that analyzes the topic.. Three people in that thread have said to log in to an administrator account, right-click the C: drive, enter its properties, click the Security tab, and then give the user permission to use the C: drive. The fix may cause problems, so if you’re even a little worried, it’s probably best to remove the update or wait for a patch.
