AirPort Express - Won't Work

I have an AirPort Express that stopped working the other day. I went to the apple store and all they could offer was buy a new one.

My Mac won't detect it. I get an message saying it needs "AirPort Utility 5.6.1" but this utility won't install on Snow Leopard.

Any solutions? Anyone experience this?

I did configure the AirPort Express on my Windows desktop and AirPlay worked via ethernet but it disappeared when I tried to connect it to my wireless network.

What type of Airport Express?

Have you tried a soft/hard/or factory reset?
Resetting an AirPort Base Station or Time Capsule FAQ

If you can connect to it via ethernet - then the Express is somewhat working. Have you tried setting it to just join the wireless network?

Also - if you can configure it using windows - then it should still work.

Here is where I am at:

Mac OS 10.6 won't find the airport express
Win OS 7 will see it I can configure it but when I try to join my network (my router) it disappears and can't locate it. I then have to reset the AirPort Express.

It is not the new AirPort Express, it is the older one.

What type of router are you trying to join it to? I think you can have it join a wireless network - but it won't extend a wireless network unless you are joining to another Airport Extreme or Time Capsule.