X box 360 Slim wifi problem?

[Vennie]

I got an xbox 360 slim awhile ago but i never set up my x box live account. I have a router that is able to connect to it but every time i try, it has a bunch of problems like i'm using a static ip address or my wep key is wrong. I triple checked everyone of these codes and they're all correct. I saw online that there are wireless adapters but i thought i didnt have to use one because the xbox 360 slim has built in wifi. Someone please tell me if i have a defective xbox or i need an adapter.