Lan/internet problem

I buyed a new pc 2 days ago. But when i connect my lan wire i get only the orange light and not the yellow light and i get network cable disconnected. Its a RJ 45 jack which is connected to a common switch. I have installed the drivers also.

MOBO is BIOSTAR TA790 GXB with AMD PHENOM 2 X2 550 BE. Vista installed.

So pls help guys.