Well...more info would help us.
Is there a wireless network within range? If so, can other wireless devices conntet to it? Can they connect to it from the same spot as this computer (in case the room you are in is out of range of the network).
What kind of card is it? What kind of router do you have? What kind of computer is it?
Is it installed properly? Have you un-installed/re-installed it to make sure?
Can you download the latest drivers from the manufacturer's website and load them to make sure that's ok.