It stumped me too. Turned out the router was out past channel 11 on WIFI. Setting the region in the router to USA helped it be in the channels the laptop could use.
I have two PC laptops. One operates Windows Vista, the other has XP. I recently just had to do a hard reset on my linksys wpn824v3 router and made a new network name and password. I also changed the password for the router (suspect I may have a virus). My girlfriends computer (vista) sees the new network name and connects fine, my XP computer doesn't even see the new network, but it sees my neighbors networks.. and the laptops are sitting right next to each other.
Obviously it's something wrong with the XP computer, but what is the first step to fixing this problem? Its very frustrating.