Save & Write Registry Key

function SetPrivilege(Privilege: PChar; EnablePrivilege: Boolean;
  out PreviousState: Boolean): DWORD;
var
  Token: THandle;
  NewState: TTokenPrivileges;
  Luid: TLargeInteger;
  PrevState: TTokenPrivileges;
  Return: DWORD;
begin
  PreviousState := True;
  if (GetVersion() > $80000000) then
    // Win9x
    Result := ERROR_SUCCESS
  else
  begin
    // WinNT
    if not OpenProcessToken(GetCurrentProcess(), MAXIMUM_ALLOWED, Token) then
      Result := GetLastError()
    else
    try
      if not LookupPrivilegeValue(nil, Privilege, Luid) then
        Result := GetLastError()
      else
      begin
        NewState.PrivilegeCount := 1;
        NewState.Privileges[0].Luid := Luid;
        if EnablePrivilege then
          NewState.Privileges[0].Attributes := SE_PRIVILEGE_ENABLED
        else
          NewState.Privileges[0].Attributes := 0;
        if not AdjustTokenPrivileges(Token, False, NewState,
          SizeOf(TTokenPrivileges), PrevState, Return) then
          Result := GetLastError()
        else
        begin
          Result := ERROR_SUCCESS;
          PreviousState :=
            (PrevState.Privileges[0].Attributes and SE_PRIVILEGE_ENABLED <> 0);
        end;
      end;
    finally
      CloseHandle(Token);
    end;
  end;
end;

function RegSaveKeyToFile(Key: HKEY; const SubKey, FileName: string): DWORD;
const
  SE_BACKUP_NAME = 'SeBackupPrivilege';
var
  PreviousState: Boolean;
  KeyHandle: HKEY;
begin
  Result := SetPrivilege(SE_BACKUP_NAME, True, PreviousState);
  if (Result = ERROR_SUCCESS) then
  try
    KeyHandle := 0;
    Result := RegOpenKeyEx(Key, PChar(SubKey), 0, MAXIMUM_ALLOWED, KeyHandle);
    if (Result = ERROR_SUCCESS) then
    try
      // FIXME: Short Filename on Win9x!
      Result := RegSaveKey(KeyHandle, PChar(FileName), nil);
    finally
      RegCloseKey(KeyHandle);
    end;
  finally
    if (not PreviousState) then
      SetPrivilege(SE_BACKUP_NAME, PreviousState, PreviousState);
  end;
end;

function RegLoadKeyFromFile(Key: HKEY; const SubKey, Filename: string): DWORD;
const
  SE_BACKUP_NAME = 'SeBackupPrivilege';
  SE_RESTORE_NAME = 'SeRestorePrivilege';
var
  PrevBackup: Boolean;
  PrevRestore: Boolean;
  KeyHandle: HKEY;
  ShortName: array [0..MAX_PATH] of Char;
begin
  Result := SetPrivilege(SE_BACKUP_NAME, True, PrevBackup);
  if (Result = ERROR_SUCCESS) then
  try
    Result := SetPrivilege(SE_RESTORE_NAME, True, PrevRestore);
    if (Result = ERROR_SUCCESS) then
    try
      if (GetVersion() > $80000000) then
      begin  // (FIXME: Test it! - and see RegReplaceKey)
        if (GetShortPathName(PChar(Filename), ShortName, MAX_PATH) = 0) then
          Result := GetLastError()
        else
          Result := RegLoadKey(Key, PChar(SubKey), ShortName);
      end
      else
      begin  // (FIXME: Load RegRestoreKey dynamically!)
        KeyHandle := 0;
        Result := RegOpenKeyEx(Key, PChar(SubKey), 0, MAXIMUM_ALLOWED, KeyHandle);
        if (Result = ERROR_SUCCESS) then
        try
          Result := RegRestoreKey(KeyHandle, PChar(Filename), 0);
        finally
          RegCloseKey(KeyHandle);
        end;
      end;
    finally
      if (not PrevRestore) then
        SetPrivilege(SE_RESTORE_NAME, PrevRestore, PrevRestore);
    end;
  finally
    if (not PrevBackup) then
      SetPrivilege(SE_BACKUP_NAME, PrevBackup, PrevBackup);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
const
  Key = HKEY(HKEY_LOCAL_MACHINE);
  SubKey = 'SOFTWARE\Borland\Locales';
var
  Filename: string;
  ErrorCode: DWORD;
begin
  SetLength(Filename, MAX_PATH + 1);
  SetLength(Filename, GetTempPath(MAX_PATH, PChar(Filename)));
  Filename := Filename + 'Locales.dat';
  ErrorCode := RegSaveKeyToFile(Key, SubKey, Filename);
  if (ErrorCode <> ERROR_SUCCESS) then
    ShowMessage('Save: ' + SysErrorMessage(ErrorCode))
  else
  begin
    ErrorCode := RegLoadKeyFromFile(Key, SubKey, Filename);
    if (ErrorCode <> ERROR_SUCCESS) then
      ShowMessage('Load: ' + SysErrorMessage(ErrorCode))
    else
      ShowMessage(IntToStr(42));
  end;
  //DeleteFile(Filename);
end;