Protect the original profile before changing it
Do not delete the affected account or its folder while it contains the only copy of personal files. Avoid registry edits unless a verified backup and another administrator account are available. Files encrypted with EFS or protected by work policy may require the original credentials or organisation support.
Identify the profile failure
| Symptom | What it suggests |
|---|---|
| “The User Profile Service failed the sign-in” | Windows cannot load the selected user profile. |
| “We can’t sign in to your account” | Windows may have loaded a temporary profile. |
| Desktop is empty and settings reset | Temporary profile, wrong account, Explorer failure or profile corruption. |
| Only one account fails | User-specific profile, permissions or registry state. |
| Every account or Safe Mode fails | Broader Windows, disk, update or hardware problem. |
1. Stop using a temporary profile for new work
Open Settings → Accounts → Your info or inspect C:\Users to confirm which profile is active. If Windows says you are signed in with a temporary profile, save any newly created work to an external drive or another confirmed location before signing out.
Do not copy temporary-profile system folders back over the damaged profile.
2. Restart and test the account once
Restart the PC fully and try the affected account again. Disconnect unnecessary storage and USB devices. Confirm that the Windows drive has free space; a nearly full system drive can prevent profile data from loading correctly.
If the problem followed an interrupted update, allow pending servicing to finish before repeated forced shutdowns.
3. Enter Safe Mode
- Hold Shift while selecting Restart.
- Choose Troubleshoot → Advanced options → Startup Settings → Restart.
- Select Safe Mode.
If the affected account opens in Safe Mode, remove only recent software strongly connected to the failure, check storage and restart normally. Safe Mode is diagnostic; it does not prove the profile is healthy.
4. Use another authorised administrator account
If another administrator already exists, sign in to it and back up accessible files from the affected profile. Do not take ownership or rewrite permissions broadly unless necessary; that can disrupt application data and encrypted content.
If no alternate administrator exists, use official recovery options. Do not download account-bypass utilities.
5. Repair Windows files and the disk
From an elevated Terminal in a working administrator account, run:
DISM.exe /Online /Cleanup-Image /RestoreHealth
sfc /scannow
Then run chkdsk C: /scan to check the online file system. Back up immediately if the SSD is disappearing, producing errors or becoming extremely slow.
6. Use System Restore after a recent system change
Open Windows Recovery Environment and choose Troubleshoot → Advanced options → System Restore. Select a restore point from before the profile failure and review affected programs.
System Restore can reverse driver, registry and system changes without intentionally removing personal documents, but a backup remains sensible.
7. Treat profile-registry repair as an advanced step
The profile mapping is stored under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList. Duplicate security identifiers, often involving a .bak entry, can indicate an incorrect profile mapping.
Registry repair must match the real SID and ProfileImagePath. Export the relevant key first and follow a verified Microsoft-supported procedure. Renaming or deleting the wrong SID can block another account, so skip this step when the mapping is unclear.
8. Create a clean profile when the original cannot be repaired
From a working administrator, create a new local or Microsoft account, sign in once to build its profile, then copy personal folders such as Documents, Pictures and Desktop from the old profile.
Do not copy NTUSER.DAT, the entire AppData tree or hidden profile-registry files wholesale; doing so can carry the corruption into the new account. Reconfigure applications individually.
9. Handle access, encryption and managed accounts carefully
Standard NTFS permissions may be corrected by an authorised administrator, but EFS-encrypted files require the matching encryption certificate. BitLocker unlocks the volume; it does not automatically decrypt EFS files inside a profile.
For domain, Entra ID, work or school accounts, contact the administrator before rebuilding the profile because policies, certificates and synced data may need a managed recovery process.
10. Investigate storage when profile corruption returns
Repeated profile damage after repair is not normal. Review Event Viewer for disk, NTFS and User Profile Service errors, run the manufacturer’s storage diagnostics and maintain a current backup. A clean profile will corrupt again if the underlying SSD, memory or file system is unstable.
Avoid these common mistakes
- Do not delete the old profile before verifying its backup.
- Do not keep important work inside a temporary profile.
- Do not change ProfileList registry entries by guesswork.
- Do not copy the complete AppData or NTUSER.DAT into a new profile.
Frequently asked questions
What causes the User Profile Service failed the sign-in error?
It can follow profile-registry corruption, an interrupted update, storage errors, security software, incorrect permissions, low free space or a damaged default profile.
Is a temporary profile safe to keep using?
No. Work saved only inside a temporary profile can be lost at sign-out. Copy important new files elsewhere and repair the original profile.
Will creating a new user account recover my old files?
A new administrator can help copy accessible files from the old profile, but application settings, encryption and permissions may require separate handling.
Technical steps align with Microsoft guidance for temporary profiles, Safe Mode, System Restore, DISM, System File Checker, user accounts and profile recovery.
Official references
For platform-specific behavior and recovery options, compare this guide with the current documentation from the relevant official source.