"Join wireless network" vs. "participate in WDS network" w Airport Express

You pose two very good questions, and ones that are not easy to answer in a paragraph or two.

You can use an AXbg to join a wireless network for the purpose of projecting your iTunes music to remote speakers or to add a remote USB printer to the network. An AXn can be used to do these things as well, but in n mode it also can use the 'Join a wireless network' configuration for another purpose—namely to serve as an Ethernet bridge to connect Ethernet-enabled devices to the network.

Both AXbg and AXn devices can do WDS (which means extending the network wirelessly), but the AXn device in n mode is easier to configure for this use by virtue of its 'Extend a wireless network' function.

My allotted two paragraphs are gone, but I would like to add that I have had limited success in using the new Ethernet bridge (also known as ProxySTA) function. I have successfully connected several Macs to the network and Internet behind an Ethernet switch connected to an AXn in Ethernet bridge mode. I even have one Windows XP SP3 successfully connected, but a Windows Vista Business SP1 computer cannot access the Internet.

I have exactly the same equipment (AirPort Extreme and 2 AirPort Express with one being a b/g and the other an n model), yet I can't get the b/g to Join Wireless Network. As soon as I do that and click the Update button, the LED begins flashing yellow and the AirPort Express disappears from the list in Airport Utility. The only way to get it to work, is to reset the AirPort Express and reconfigure it to participate in WDS network.

Essentially, what I'm trying to do is the following:

AirPort Extreme distributes my Cable Modem Internet connection
AirPort Express "n" extends the wireless network AND connects to an audio device for AirTunes
AirPort Express "b/g" connects to a different audio device for AirTunes, but doesn't extend the wireless network

I want to connect a xbox360 via an ethernet cable and plugging this into an airport express b/g device. I need simple (I'm like that) instructions on how to enable wds and the bridge function. Can anyone talk me through the process if I'm right in assuming this will work? I have an airport extreme n base station and I would really like a walkthrough for both devises.

I'm going to piggy back onto this, if that's ok. I have:

•Airport Extreme in n only mode connected to my cable modem set to allow network to be extended.
•An AXn in another room on my main network that is also set to allow network to be extended.

I want to plug my powermac via ethernet to the AXn. It gets an ip and can see other local machines, but it can't get to the internet. I'm not sure the AXn is connected correctly? Any ideas?