It may be two things. Either:
1) SSID
Wireless networks have a unique name called an SSID. It is good security practice to hide this once you have set up the network as it means it wont show up in the network list.
Unhide the SSID in your wireless router config and then connect the laptop to it. Once it is connected sucessfully then hide the SSID again
2) MAC
Most people secure there network by using a MAC adress filter. A MAC adress is unique to a single network card. Therefore, If you are using a different card you may not able to connect to the network. Check the MAC adress options in your wireless routers config and add the adress of your new card to it (to find out a cards MAC adress in XP right clickm on the connection -> support tab -> details button)