Dell xps 420 Can not find the an ip address- please help

Hello,

I have a Dell 420 xps desktop running windows Professional 7.
I have a hard wired connection directly into my AT and T wireless router.

my dell can not connect to the internet. says there is no internet connection.

I have other computers on the network that connect just fine on the same router

I have also checked and dhcp is not enabled.

in the 4 tcp and the 6 tcp settings they are both set to get ip address automatically.

and i think i have the latest driver for the motherboard,

i have aslo changed the ethernet cable.

still no go .

i am really at a loss...

if anyone can help I would truly appreciate it.

thanks