This is a tip which should be also available for my international readers, therefore it is in english 🙂 If you prefer a german version, please click on this Macwelt article.
My father uses my old Apple Airport Express 1st Generation. He uses Mountain Lion aka. Mac OS X 10.8 on his Macbook Pro and wanted to reconfigure the Airport. However, Apple decided to drop support for older generations of the Airport Express. Therefore, the current version 6.1 of the Airport Utilities is unable to find his Airport Express model.
This is where this handy tool come into play. With unpkg, you can extract the content of the pkg installers supplied by Apple, as older Versions are not runnable on Mountain Lion. You need to extract the tool and start it.
Now you can download the older Airport Utilitiy in version 5.61 which is the last version with support for his type of Airport Express. You can download it directly from Apple. Mount the downloaded dmg file and drag the Airport Utility Installer onto the unpkg window. unpgk will now decompress the pkg file to your desktop.
You can now move the App from the Applications/Utilities folder to your Application folder. Double click on it and you will get the older version of the utility. Be sure to skip the update, as it will try to download the newer version of the Airport Utility 6.1 which you definitively don’t want to use as it will stop working with your kind of Airport Express.