The Base Station Extras folder on the AirPort disc no longer includes a separate file for AirPort Base Station Software.
Rather than opening this file directly, you may get the same effect by using the AirPort Admin Utility or the AirPort Setup Assistant. Either of these applications prompts you to update the software on your base station when it is using an earlier version.
Note: Wireless Internet access requires an Internet service provider (fees may apply) and AirPort (or AirPort-compatible) wireless Ethernet card and base station. Some ISPs are not compatible with AirPort. For more information, see technical document 106590: "
AirPort: Requirements for Wireless Internet Access"