ERROR_DS_UNDELETE_SAM_VALIDATION_FAILED 0x800721C5

Error code 8645 · HRESULT 0x800721C5

WINDOWS

The undelete operation failed because the Sam Account Name or Additional Sam Account Name of the object being undeleted conflicts with an existing live object.

Windows troubleshooting diagram: Device Manager warning and a system file scan
Windows errors: check drivers, system files and Event Viewer, in that order.

What it means

ERROR_DS_UNDELETE_SAM_VALIDATION_FAILED is a Windows error code (system error 8645, returned as HRESULT 0x800721C5) reported by Windows. Its official message is: “The undelete operation failed because the Sam Account Name or Additional Sam Account Name of the object being undeleted conflicts with an existing live object.”

How to fix ERROR_DS_UNDELETE_SAM_VALIDATION_FAILED

  1. Reboot once — many one-off system codes disappear with a clean restart
  2. Repair system files: 'sfc /scannow' then 'DISM /Online /Cleanup-Image /RestoreHealth'
  3. Find the source in Event Viewer → System: filter for this exact code and open its provider link

Related errors

ERROR_DS_LOW_ADLDS_FFLERROR_DS_SPN_VALUE_NOT_UNIQUE_IN_FORESTERROR_DS_HIGH_DSA_VERSIONERROR_DS_UPN_VALUE_NOT_UNIQUE_IN_FORESTERROR_DOMAIN_SID_SAME_AS_LOCAL_WORKSTATIONERROR_INCORRECT_ACCOUNT_TYPEERROR_DS_HIGH_ADLDS_FFL

Source: Microsoft WinError.h

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