If the archive asks for a password, check the site where you originally found the links; it is usually listed there.
To get the game files out, you cannot just open part 19 by itself. You need to follow these steps:
If you get an error specifically mentioning "part 19," that specific file is likely corrupted. You will need to redownload just that piece.
If the extraction stops and asks for a "volume," it means you are missing one of the parts in the sequence.