Microsoft is investigating a new issue affecting some Samsung laptops running Windows 11 after installing the February 2026 security updates, in which users lose access to their C:\ drive and are unable to launch applications.

The company says it is working with Samsung to determine whether the problem is related to the Windows updates or Samsung software installed on affected devices.

"Users might encounter the error, 'C:\ is not accessible – Access denied', which prevents access to files and blocks the launch of some applications including Outlook, Office apps, web browsers, system utilities and Quick Assist," explains Microsoft.

Microsoft says these errors can appear during normal Windows usage on a Samsung device, such as when accessing files, launching applications, or performing administrative tasks. In some cases, the permission problems can prevent users from elevating privileges, uninstalling updates, or accessing logs.

The problem has been reported mostly in Brazil, Portugal, South Korea, and India, and is primarily impacting Samsung Galaxy Book 4 and other Samsung consumer devices.

Microsoft says its latest investigation suggests the issue may be related to the Samsung Share application, though the exact root cause has not yet been confirmed.

At this time, the issue only impacts systems running Windows 11 version 25H2 and 24H2.

While Microsoft has not shared a temporary solution, a Reddit user claiming to be a Samsung technician in Brazil has posted a workaround that some affected users say restores access to the C:\ drive.

However, the workaround requires changing the ownership of the entire C:\ drive and all subfolders to the "Everyone" group, including system directories and files that are normally owned by TrustedInstaller or SYSTEM.

Changing ownership of system files in this way weakens Windows' built-in security protections. Therefore, users should avoid applying the workaround unless absolutely necessary and instead wait for a fix from Microsoft.