aiport and xbox live

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ok, so i have a network set up, with an aiport extreme with a wireless network going to 2 laptops and a few ipod touches, and on wired connectiong from that aiport extreme. and i have an old aiport express, and i wan't to use it to connect to xbox live, as a bridge(i think) so that the AP extreme will send a wireless signal to the express and then from the express to the xbox via ethernet cable, but it is no working, i have the airport set to join my existing network, and i can play music from my computers through speakers via my aiport express, but the xbox cannot detect the aiport at all, any tips? i know this may be confusing, but i am not the most knowledgable when it comes to networking, so laymens terms would be appreciated. also let me know if you don't understand something