If it was working fine before, it should be working fine now so would have whatever is used to have. Or are you saying you had an old one that was working but your new one is not? How are you trying to connect and are you getting any error messages? You may need to re-word your question. Maybe just say what issue you are having.
Wireless notebooks need a modem as in a ADSL moden. If you have one of those that is all it needs. They will work with a dial up modem as well since alot/most have a RJ 11 port for a phone line to plug directly into the notebook and if they do not then you can just plug the ADSL line into the ADSL moden and then run the ethernet cable from the modem to the notebook to obtain a wired network connection.
To get the wireless connection which im guessing you already had im guessing you already had a SSID set up and that it was working. If that is the case then either the modem/router that your were getting the connection from as failed or the network card on the notebook has failed since you can no longer connect.
Just to double check run command prompt ( search for cmd in vista of win7 in the start menu search menu) and run ipconfig /all and see what ip address has been assigned to your wireless NIC ( network interface card ). If it is a 169.254.xxx.xxx address then you router is no longer assigning private ip addresses to your system and it is getting an APIPA address.
IF it is a 192.168.xxx.xxx then the modem is assigning a ip address to the computers that are connected to it.
What operating system are your running. If its XP i can not remember how to do it but if it is VISTA of WIN7 then down next to the clock click on your network icon and open your netowrk and sharing centre. Then on the LEFT PANE select change adapter settings and double click on you wireless connection. Then select properties and then double click on internet protocol version 4. Once in click the use the following IP address check box and enter IP address: 192.168.1.10 . Subnet Mask: 255.255.255.0 . Default Gateway 192.168.1.1 . Do not worry about the DNS option. Doing this should eliminate the DHCP on the MODEM and determine if it is the NIC on the NOTEBOOK or the actual MODEM