Q: i cannot install airport utility 5.6 onto my computer although i need it to configure an older airport express and base station

http://macintoshdesktop.blogspot.co.uk/2012/12/airport-utility-56-and-mountain-l ion.html

Here is my method.. the software is free that is required.. always a good point.

How to load 5.6 into ML.

1. Download 5.6 for Lion.

http://support.apple.com/kb/DL1482

Click to open the dmg but do not attempt to install the pkg.. it won't work anyway.

2. Download and install unpkg.

http://www.timdoug.com/unpkg/

Run unpkg on the desktop.. it is very simple.. drag the AirPortUtility56.pkg file over to unpkg.. and it will create a new directory of the same name on the desktop.. drill down.. applications utilities .. there lo and behold is Airport utility 5.6 .. drag it to your main utilities directory or just run it from current location.

You cannot uninstall 6.1 so don't try.. and you cannot or should not run them both at the same time.. so just ignore the toyland version.. the plastic hammer.. and start using 5.6.. a real tool.

For screen shots see this post.

https://discussions.apple.com/thread/4668746?tstart=0

Or restore Airport Utility 5.6.1 from your time machine backup before ML install.  Works as well.