So I just recently purchased a second Airport Extreme as an extender to my current one which is located in my basement. I have an external disk plugged into the main AE, but want to plug in another disk into the AE that's extending my network so my wife can back her MBP wirelessly with Time Machine. The issue is that the second AE is not even showing up in Finder and it's not recognizing the external drive that's plugged into it. I can see my main AE router and hard disk just fine in Finder. So can the second AE be used to to backup my wife's mac with another external disk or does that feature only work with the main AE?