I assume by "new airport express" you are referring to the 2nd generation 802.11n AirPort Express Base Station (AXn). What model is your "original airport express?" Is it a 1st generation 802.11n or a 802.11g model?
If it is the former, please refer to the following Apple Support article for details on how to configure an extended network. On the other hand if it is an 802.11g model, check out this Apple Support article instead.
Hi Tesserax, thanks for replying. The new express is the 'n' and it is currently running wifi fine and all my gadgets can see it. The old express is a 'g' and I need utility 5.6 for that which will not install on my OS 10.8.2. The work around I found to strip out the installer also doesn't work, I just get a shell script error.
So my utility 6.1 can see the old AE 'n' but when I select it to configure it, it says I need utility 5.6. That doesn't install so I am stuck.