I recently purchase an Airport Extreme to get the 'N' coverage my Home Hub doesn't provide. As I have BT Vision (works very, very well) I couldn't scrape my Home Hub.
I have a number of computers that need to hang of this not least my XBOX 360 and PS3 (bluray player not games machine note) so I approached this with a little trepidation. My computers are a mixture of Wintel PC's and Laptops + 3 MAC's (note each also runs Vista).
Advice from my friendly MAC shop was just to use the supplied Airport config program.
This worked a dream allowing me to setup both my hub and new Airport Extreme auto configuring bridge mode and giving me the option of shutting down my Home hub wireless.
In the end I selected the option for my Extreme to just support 'N' and the Homehub to support the rest.
All worked first time.....
Re-booting my MacBook Pro into Vista mode I was immediately able to connect to my Airport Extreme. All works a dream...
Thanks Apple for making it so simple.....