Seems to be because that model of Mac can only use an AirPort (802.11b) card.

Here is the compatible computer list for Airport Extreme cards:

http://docs.info.apple.com/article.html?artnum=107440

Here is the compatible computer list for Airport cards.

http://docs.info.apple.com/article.html?artnum=106777

Note that your computer is on the latter list..

And I thought I'd done my research. Thank you so much for these links. I've grumbled to Apple, pointing out that the product pages in their online Store do not give links to these supporting pages, and that their compatibility para is ambiguous. He says he will pass my comments on . . . mmmm.

Meanwhile, a full refund is promised against the returned goods.

That leaves me with a home wireless network still to set up:

PPC G4 (467 MHz) + iMac PPC G3 (500 MHz) + PC (Windows XP, with Wi-Fi card fitted)

How would you network them? Do I have to use AirPort equipment (the 'original' that is, not Extreme!), or can I use non-Mac stuff? A very basic question.

Feeling very confused by it all.

Many thanks for your time and trouble.

I concur, the pages for AirPort are ambigious about what hardware supports what wifi hardware. I had to dig a little to find what I did.

No, you don't have to use Apple's AirPort Base Station stuff at all. I'd just go ahead and buy the AirPort (802.11b) cards from Apple, install them in your Macs. Supposedly they are rebranded Orinoco (sp?) WiFi cards, but I'm totally unsure of that, and don't want to steer you in the wrong direction. I can tell you, unequovocably, that AirPort and AirPort Extreme cards work just fine with 3rd party wifi acess points/wifi routers. I have a NetGear WGR614v3 (It's a mixed 802.11b & 802.11g) at home that does a pretty good job doing the wifi router thing for my APExtreme equipped PowerBook.

I have an old i Mac that is on the list for compatibility with the AirPort card, however, on the apple support website article for 'AirPort Extreme Card: Compatible Macintosh computers' it says "The AirPort Extreme Card works with the computers listed below(mine isn't listed on the compatible i macs link) and with Mac OS X 10.2.3 or later (which mine does have)."

so my question is, does the compatibility for the AirPort extreme card rely on if your computer is new enough to use it, or does having a later operating system mean that it will work?

Thanks,
rabskins