Wireless Lan connected but no Internet

I am using 2 similar type of laptop that is running on Windows Vista but on laptop X I am not able to get to internet over wireless, and on laptop Y, there is no problem with the wireless at all. If I am connecting Laptop X to a wired lan ethernet cable then internet is working properly but if I unplug the cable and use wireless then all I get is local lan and nothing else? I did a internal ping test which works fine, external request is timing out. I have also uninstalled Norton Internet Security antivirus and firewall and also disabled Windows Firewall and DEP but to no avail? Can anyone tell me how do I solve this issue? Thanks

It might be that you dont have a valid wireless connection between the computer and the router. You can also try to use the Xirrus Wi-Fi Inspector that is a powerful tool for managing and troubleshooting the Wi-Fi on a Windows XP SP2 or later, Vista laptop. Built in tests enable you to characterize the integrity and performance of your Wi-Fi connection.

Thanks for the reply, but an intereseting part was that the new modem in default mode fixed the internet problem for me. I also followed a clean setup with dsl and then router and then laptop x using the ethernet or wireless and both of this thing worked for me.