Belkin wireless g gaming adapter connection to xbox 360

i have a 2wire router/gateway (model no. 2701HG-B) that was sent to me from AT&T for my broadband connection. It is connected to my pc via ethernet. i can connect to my router with my ps3 wirelessly without a problem and play online. but everyone knows the xbox 360 cant do that. so my friend gave me his belkin wireless G gaming adapter (model no. F5D7330) and im supposed to connect that to the xbox 360 via ethernet and its supposed to make a connection with my 2wire router wirelessly, so that i could play online. but it would link up as wired since the adapter is connected to my xbox via ethernet. my problem is everytime it gets to the ip address it fails. i noticed that during the setup with the disc that he just now gave me that my router and adapter arent making a connection to one another. how do i establish a connection. i dont know which is the problem. the adapter makes a wireless connection to someone elses router, but my ps3 makes a wireless connection to my router. so im not sure why a wireless connection cant be established between my router and my adapter. can anyone help me out.