I wanted to connect a (fairly old) laptop running Windows XP to my home wireless router the other day. With WEP discredited, I have the security on the router set to WPA2. Since the laptop doesn’t have inbuilt WPA2 support, I bought a new WPA2 wireless LAN adapter. After installing the the accompanying software and plugging in the adapter to one of the USB sockets, I tried to set up the connection – and failed. When I scanned for wireless networks, the network was visible, but nothing I did could persuade the laptop join it.
An email to the manufacturer’s support desk brought the answer. Windows XP doesn’t have WPA2 support included by default. To enable it, you must install the KB893357 update. Once I did that, I connected with no further problems.