From X-Plane Wiki

You should first try to install using the installer on your DVD. However, if that installer does not work, these installers can help.

[edit] Installers for X-Plane 9 DVDs.

The current DVD installer for X-Plane 9 is version 2.01. This installer will work on any X-Plane 9 DVD. You can download it with these links:

• Linux DVD Installer
• Mac DVD Installer
• Windows DVD Installer

[edit] Installer for X-Plane 8 DVDs.

The current DVD installer for X-Plane 8 is version 1.23. This installer will work on an X-Plane 8 DVD versions 815 through 860.

• Linux DVD Installer
• Mac DVD Installer
• Windows DVD Installer

See Installer Versions for more info.