I have a big problem with WiFi in Dell 1525

Hi all friends,

I buy a new Dell laptop, Inspiron 1525 and have a big problem with WiFi in the windows... XP and Vista...

All the Drivers are installed in my laptop... but WiFi not work (and blue LED not light up) ... just when the laptop restarted before the uping the windows the wifi led is on, when the windows start led is off and can not search any networks...
what is this problem... i prefer to solve this problem in win xp.

thanks so much

Majid