I have a BT Router and it works great with both desktop and laptop. I am no expert so I apologise if my response is not what you are looking for. (I remember the nightmare I had setting the system up!)
Have you set up the WEP key that protects the network, and which allows the laptop to identify the router signal?
Have you set the network up as 'open' or 'shared'?
If the WEP is setup and its is set to 'shared' it should work OK.