By default, Windows XP does not has native support for WPA in Windows XP (which only added via KB815485 WPA support patch and via Service Pack 2), and no native support for WPA2 until Windows XP SP3.
To verify that the unable or cannot connect to the wireless network is indeed cause by lack of support in Windows XP, right click on the Network Connections icon on the system tray (notification area), then go to Wireless Network tab.
In this case, fallback to WEP encryption, or get a new wireless adapter.
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Troubleshooting Tools in Windows Wireless AP Troubleshooting Tools IAS Troubleshooting Tools Troubleshooting IAS Authentication and Authorization Summary Related Links The tools for troubleshooting wireless connections in Windows XP and Windows Server 2003 are the Network Connections folder and tracing.
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.WPA2 certification is now mandatory for network devices to be certified by Wi-Fi Alliance as “Wi-Fi CERTIFIED”.The Windows XP (with or without SP1) system does work properly and connect perfectly to the wireless network if the router, WAP (wireless access point) is configured to enable and use WEP 64-bit/128-bit/225-bit security encryption, which is less secure than WPA2 and WPA.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.If an authentication requires additional information from the user, such as selecting one of multiple user certificates, a text balloon appears instructing the user.Within the Network Connections folder, the text under the name of the connection corresponding to the wireless network adapter indicates the status of the connection.As mentioned just now, operating system support for wireless security protocol especially WPA2 is just a piece of the jigsaw puzzle.The PC must also has client wireless card, or built-in wireless receiver, or Wi-Fi network adapter that supports WPA and WPA2.Beside, in Windows XP SP1 computer, the WPA encrypted wireless network can be connected without error too.The error only surface on pre-SP2 Windows XP on both WPA and WPA2 protocols, and WPA2 on Windows XP SP2.