To let Windows XP pre-SP2 system provides support for WPA Wi Fi network security encryption method, download and install KB815495 (KB article), or upgrade to Windows XP SP2.
To provides operating system support for WPA2, download and install the newer KB917021 Wireless Client Update for Windows XP with Service Pack 2 (validation required at Microsoft Download Center, or user can direct download the Windows XP-KB917021-v3-x86-ENU.exe) or older KB893357 Wi-Fi Protected Access 2 (WPA2) and Wireless Provisioning Services Information Element (WPS IE) update for Windows XP SP2 (validation required at Microsoft Download Center, or user can direct download the Windows XP-KB893357-v2-x86-ENU.exe) or more recommended, upgrade to Windows XP SP3, which now incorporates the WPA2 hotfix and implements the WPA2 IEEE 802.11i wireless networking standard natively.
When a wireless client running Windows XP with SP2 or Windows Server 2003 with Service Pack 1 attempts a wireless connection, it goes through the following authentication states, which are indicated as the status of the wireless connection in the Network Connections folder, and in the new wireless connection Status dialog box, and in the Wireless Network Connection dialog box: Once authentication has succeeded, a wireless client running Windows XP with SP2 or Windows Server 2003 with Service Pack 1 then attempts to obtain a valid IP address configuration and goes through the following states, which are indicated as the status of the wireless connection in the Network Connections folder, and in the new wireless connection Status dialog box, and in the Wireless Network Connection dialog box: These improvements give the user and the network troubleshooter more information about how the wireless connection is progressing, from the initial association to the allocation of a valid IP address.
If the wireless connection obtains an APIPA address, Windows XP with SP2 and Windows Server 2003 with Service Pack 1 warns you with the following message in the notification area of the desktop: "The connection has limited or no connectivity.
After configuring the security settings of a wireless 802.11a/b/g router or access point (AP) to enable WPA or WPA2 encryption with a Pre-Shared Key (PSK or WPA-Personal/WPA2-Personal), or Radius Server (WPA-Enterprise/WPA2-Enterprise), Windows XP machine cannot or unable connect to the WPA security-enabled wireless network (although Windows XP is able to scan and detect the availability of the Wi-Fi network) with the following error message: Windows is unable to connect to the selected network. Please refresh the list of available networks, and try to connect again.