Make an Ubuntu Linux live USB drive using
this utility. (Please, be careful.) Google 'how to boot from usb drive ___insert_laptop_model_here__
_'. Boot from the flash drive and try connecting to a network.
If Ubuntu doesn't recognize the wireless radio, either there's a hardware problem or Ubuntu doesn't have built-in drivers for that particular radio. If the latter is the case, you can find some Linux drivers online and install them thru apt-get.
If Ubuntu recognizes the radio but can't connect, it's probably a hardware issue, meaning you may be SOL. You may have to crack open the laptop and reseat the adapter or blow off any accumulated dust. If that doesn't work, your wireless card may be dead.
If Ubuntu recognizes the radio and connects, it's a problem with Windows. My money is on this one.