How to fix Error 1304 on Windows 11

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Troubleshooting Guide: Error 1304 – LAN Manager Password Conversion Failure

Why This Error Happens

This error occurs because the password contains characters, symbols, or a length that exceeds what the legacy LAN Manager (LM) hash format can support, since LM hashing was designed for older, less complex password schemes. Windows 11 attempts to generate this legacy hash for backward compatibility purposes, but when the password is too complex, it returns a NULL string instead of a valid hash. This typically surfaces when changing passwords on systems that still have LM hash generation enabled via local security policy or registry settings.

Step-by-Step Resolution Guide

Step 1: Disable LAN Manager Hash Storage via Local Security Policy

  • Press Win + R, type secpol.msc, and press Enter to open the Local Security Policy editor.
  • Navigate to Security Settings > Local Policies > Security Options.
  • Locate “Network security: Do not store LAN Manager hash value on next password change”.
  • Set this policy to Enabled, then click Apply and OK.

Step 2: Modify the Registry Directly (If Group Policy Editor Is Unavailable)

  • Press Win + R, type regedit, and press Enter.
  • Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa.
  • Create or modify a DWORD value named NoLMHash and set it to 1.
  • Restart the machine for the registry change to take effect.

Step 3: Change the Password After Applying the Policy

  • Log in with an administrator account and navigate to Settings > Accounts > Sign-in options.
  • Select the affected user account and choose Change Password.
  • Enter a new password (ensuring it meets organizational complexity requirements) to trigger a fresh hash generation without the LM format.

Step 4: Clear Cached Credentials (If Error Persists)

  • Open Command Prompt as Administrator.
  • Run net user [username] * to reset the password directly via CLI, forcing Windows to regenerate credential hashes.
  • Reboot the system to ensure the Local Security Authority (LSA) reloads the updated policy.

Alternative or Verification Steps

  • Verify the fix by checking the registry value NoLMHash under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa remains set to 1 after a reboot, and confirm no Error 1304 appears in the Event Viewer under Windows Logs > System.
  • If the issue persists, use gpupdate /force in an elevated Command Prompt to ensure the Group Policy change has been fully applied across the system.