Finding an update for a piece of hardware from 2005 can be nearly impossible on a manufacturer’s modern, streamlined website. Open directories often mirror old FTP sites that still house these "extinct" files.
An "Index of" page is a default display generated by web servers (like Apache or Nginx) when there is no index.html or index.php file in a folder. Instead of a styled website, the server simply lists every file stored in that directory.
Run any downloaded .exe or .upd files through a robust antivirus or a service like VirusTotal before execution.