Microsoft: Windows 11 users can't access C: drive on some Samsung PCs

Microsoft is investigating a new post-update issue affecting some Samsung Galaxy Book and other Samsung consumer devices running Windows 11 (24H2 and 25H2) after February 2026 security updates, where users receive 'C:\ is not accessible – Access denied' errors that block access to files, applications (Outlook, Office, browsers) and some administrative actions; Microsoft is working with Samsung and suspects the Samsung Share application may be related, no official workaround has been provided and a publicly-shared fix that reassigns C:\ ownership to Everyone is unsafe and discouraged.