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My question is - right now the Powermac is the main CPU concerning Airport administration. My PC and our other iMac are networked, and now, so is the new iMac. Ultimately, I will be moving the G5 to the basement, assuming I keep it at all, and need to know how to transfer the Airport administration stuff from it to the new iMac. Can anyone help?
Assuming that you are still planning to use Migration Assistant, the network settings will be transferred to the new Mac if you choose to do so. There is no need to transfer individual preference files. And if you should happen to name the new Mac the same as the old Mac, OS X is smart enough to rename the old Mac "Old Name 1" so that the old Mac can access your network without complications. Sweet! You can "administer" your network from either Mac if you wish after the file transfer.
No offense intended, but you have been asking a lot of basic questions regarding your Mac. I recommend getting a copy of David Pogue's "Missing Manual" for Tiger (or Leopard, but the Tiger manual should do the trick since the Leopard edition presumably isn't out yet...) Pogue does an excelent job of covering both the basics and more advanced topics and he writes with minimal jargon and (thankfully!) with a sense of humor. You can learn the basics and get answers to most of your questions quicker than posting a question and then waiting for a reply at TS.
My friends and clients that have purchased a Missing Manual and read it have gained a better understanding of how their Mac works and tend to have few, if any, problems with their Macs. They also become better at diagnosing and correcting glitches on their own. That can be very handy when one is facing a deadline and help isn't readily available at your fave online forum.