get windows key

.pas

const
  CharMap: array [0..23] of char = 'BCDFGHJKMPQRTVWXY2346789';
var
  ProductID: array of byte;
  IdPart: array [0..14] of byte;
  Registry: TRegistry;
  DataSize: integer;
  Key: ansistring;
  i, j, c: integer;
begin
  Registry := TRegistry.Create;
  try
    Registry.RootKey := HKEY_LOCAL_MACHINE;
    if Registry.OpenKeyReadOnly('SOFTWARE\Microsoft\Windows NT\CurrentVersion') then
    begin
      key := '';
      DataSize := 0;
      DataSize := Registry.GetDataSize('DigitalProductId');
      if DataSize > 0 then
      begin
        SetLength(productID, DataSize);
        FillChar(IdPart, 15, 0);
        Registry.ReadBinaryData('DigitalProductId', Pointer(productID)^,
          Length(productID));
        Move(Pointer(productID[52])^, Pointer(idPart[0])^, Length(IdPart));
        i := 0;
        j := 0;
        while i < 25 do
        begin
          c := 0;
          j := Length(IdPart) - 1;
          while j >= 0 do
          begin
            c := (c shl 8) xor idpart[j];
            idpart[j] := byte(c div 24);
            c := c mod 24;
            Dec(j);
          end;
          if (i > 0) and (i mod 5 = 0) then
            key := key + '-';
          key := key + charmap[c];
          Inc(i);
        end;
      end;

    end;
    Memo1.Lines.Clear;
    memo1.Lines.Add(key);
  finally
    productID := nil;
    Registry.Free;
  end;
end;