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Microsoft documented a serious C: drive access problem on some Samsung PCs running Windows 11 24H2 or 25H2, but its investigation with Samsung traced the cause to the Samsung Galaxy Connect app—not to Windows updates. The issue appeared after the February 10, 2026 update KB5077181 or later updates and produced the message “C: is not accessible – Access denied.” Microsoft published a recovery procedure and marked the issue resolved externally on March 16, 2026. If your symptoms match, use Microsoft’s official repair instructions, rather than blindly uninstalling a Windows security update.
What happened—and what Microsoft says caused it
After users installed the February 10, 2026 Windows security update KB5077181, or a subsequent update, some Samsung PCs began denying access to the system drive. The error read C: is not accessible – Access denied. Users also reported that applications and administrative actions stopped working.
The timing made the Windows update an obvious suspect. Microsoft and Samsung investigated and concluded that the problem was caused by Samsung Galaxy Connect, also called Samsung Continuity Service in Microsoft’s recovery guidance. Microsoft says the issue was not caused by the current or previous Windows monthly updates. The update and the failures coincided; that does not make the update the confirmed cause. Microsoft’s release-health notice lists the issue as resolved externally.
Microsoft opened its release-health entry on March 13, 2026. Mitigations began March 14, including temporarily removing the affected Galaxy Connect app from the Microsoft Store and republishing a stable previous version. Microsoft published recovery instructions on March 16 and marked the issue resolved externally that day. As of August 18, 2026, this is a resolved, narrowly scoped Samsung software and permissions incident—not an active, universal Windows 11 failure. Removing or republishing the app helps prevent further cases; a PC whose permissions were already damaged may still need the recovery procedure.
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Who was affected?
Microsoft documented the issue on Windows 11 versions 24H2 and 25H2, across editions. It observed it on some Samsung Galaxy Book 4 systems and Samsung desktop models, including:
NP750XGJ,NP750XGL,NP754XGJ,NP754XFGandNP754XGKDM500SGA,DM500TDA,DM500TGAandDM501SGA
This list does not mean every unit of those models was affected, and Microsoft has not published an affected-device count. Nor is there evidence that all Galaxy Books, all Samsung PCs or Windows 11 PCs generally were affected. The advisory describes a specific Samsung app and permissions problem.
Symptoms to check
The clearest sign is the exact C: drive message: C: is not accessible – Access denied. Microsoft also documented these related failures:
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- Files on the C: drive would not open.
- Outlook, Office apps, browsers, system utilities or Quick Assist would not launch.
- Administrative tasks failed, or Windows would not elevate privileges.
- Uninstalling updates or collecting logs became difficult.
The issue could surface during ordinary use; Microsoft says it did not require a special action beyond routine operations. The combination of the exact error, an affected Samsung model, Windows 11 24H2 or 25H2, and Galaxy Connect or Continuity Service makes the official recovery route relevant.
Is the SSD or hard drive failing?
Not necessarily. Microsoft describes this incident as a permissions problem, and says its repair restores Windows’ default permissions without accessing or modifying personal files. The documented symptoms are not proof of physical storage failure.
Treat other warning signs separately. If the drive disappears from BIOS/UEFI, disconnects intermittently, reports SMART or storage-controller errors, makes unusual noises, or has unrelated read/write failures, back up what you can and seek qualified help. If the data is business-critical and there are additional signs of drive trouble, avoid experimenting with permissions and consider a professional recovery provider.
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Microsoft’s official recovery procedure
Microsoft published the procedure in KB5084914. Microsoft says it takes about 10–15 minutes and requires an administrator account. It uninstalls the Samsung app, temporarily changes drive ownership and permissions, runs a Microsoft-provided icacls batch file, and restarts the PC. These are Microsoft’s documented steps, not independently tested instructions.
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If you are uncomfortable changing drive permissions, Microsoft recommends contacting Samsung Support and asking for the “C: drive permissions restore” procedure. If files are still accessible through another account, copy essential data to an external drive or trusted cloud location first. Do not assume cloud sync completed if the files cannot be opened.
1. Uninstall the Samsung app
- Open Start > Settings.
- Go to Apps > Installed apps.
- Find Samsung Galaxy Connect or Samsung Continuity Service, select it and choose Uninstall.
- Restart the PC.
2. Temporarily change ownership of C:
- Open File Explorer and select This PC.
- Right-click Local Disk (C:), choose Properties, then open Security > Advanced.
- Next to Owner, select Change.
- Enter
Everyone, confirm, and select Yes if prompted.
3. Add the temporary permission
- In the C: drive Properties window, select Security > Edit, then Add.
- Enter
Everyoneand select OK, then Yes if prompted. - If multiple security alerts appear, press Alt+C to continue.
Important: The temporary Everyone entry is part of Microsoft’s recovery sequence. Do not leave broad Everyone permissions in place as a general configuration.
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4. Create the repair batch file
Open Notepad and paste the following commands exactly as Microsoft supplies them:
icacls c: /grant *S-1-5-32-544:(OI)(CI)(F)
icacls c: /grant *S-1-5-18:(OI)(CI)(F)
icacls c: /grant *S-1-5-32-545:(OI)(CI)(RX)
icacls c: /grant *S-1-5-11:(OI)(CI)(IO)(M)
icacls c: /grant *S-1-5-11:(AD)
icacls c: /setowner *S-1-5-80-956008885-3418522649-1831038044-1853292631-2271478464
icacls c: /remove *S-1-1-0
pauseSave the file to the Desktop as RestoreAccess.bat. In Notepad’s Save dialog, set Save as type to All Files; check that Windows has not appended .txt, leaving a filename such as RestoreAccess.bat.txt. The commands use security identifiers (SIDs) instead of localized account names. Microsoft’s instructions use them to restore permissions for Administrators, SYSTEM, Users, Authenticated Users and TrustedInstaller, then remove the temporary Everyone entry.
Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problems5. Run it and restart
- Right-click
RestoreAccess.baton the Desktop and select Run as administrator. - Approve the User Account Control prompt and wait for the process to finish.
- Restart the computer.
Microsoft says the expected result is that C: opens normally, system behavior returns to normal, and ownership is restored to Windows’ TrustedInstaller service. The procedure does not access or modify personal files, according to Microsoft. That is the expected outcome for this documented incident, not a guarantee for every cause of an access-denied error.
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Should you uninstall KB5077181?
Do not make uninstalling the Windows update your first response. Microsoft’s final finding points to Galaxy Connect or Continuity Service, and the documented recovery path removes that app and repairs permissions. Removing a security update also removes its fixes, and a permissions failure may prevent you from elevating privileges to uninstall it in the first place.
What not to try
- Do not copy random
takeownoricaclscommands from forums or alter Microsoft’s batch file. - Do not grant Everyone permanent full control or leave ownership assigned to a personal account.
- Do not format the system drive, delete the Windows directory or reset Windows before considering the official recovery route.
- Do not use registry cleaners, generic “permission repair” utilities or PC optimizers for this issue.
- Do not assume that removing the update will restore C: access.
If the symptoms do not match—or the repair cannot run
Microsoft’s notice covers a narrow Samsung-and-app scenario. Look for another diagnosis if the PC is not one of the identified Samsung models, the error is on another volume such as D: or an external drive, Galaxy Connect or Continuity Service is not installed, Windows cannot boot, BitLocker is requesting a recovery key, or the drive is missing from firmware. Malware, a failed disk clone and manual permission changes can also cause separate access problems.
If you cannot sign in with an administrator account, cannot launch the required tools, encounter a UAC failure, or still cannot access C: after the temporary permission change, do not improvise with recovery-environment commands. Microsoft’s documented fallback is to contact Samsung Support and reference the C: drive access issue involving Galaxy Connect; provide your model number, Windows version, exact error and recent update history. For Windows troubleshooting outside this specific Samsung incident, use Microsoft Support.
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