Microsoft Knowledge Base Article 893357 contains the following summary and introduction:

Summary

This article describes the Wi-Fi Protected Access 2 (WPA2)/Wireless Provisioning Services Information Element (WPS IE) Update. A link to download this update is included. You can install this update on a computer that is running Windows XP with Service Pack 2. The update supports the additional mandatory security features of the IEEE 802.11i standard that are not already included for products that support WPA. Additionally, after you install the update, Windows XP will display previously hidden Service Set Identifiers (SSIDs) in the Choose A Wireless Network dialog box. This functionality makes it easier for you to connect to public Wi-Fi networks to which you have not previously connected.

INTRODUCTION

The Wi-Fi Protected Access 2 (WPA2)/Wireless Provisioning Services Information Element (WPS IE) Update for computers that are running Microsoft Windows XP with Service Pack 2 (SP2) is available. This update enhances the Windows XP wireless client software with support for the new Wi-Fi Alliance certification for wireless security. The update also makes it easier to connect to secure public spaces that are equipped with wireless Internet access. These locations are otherwise known as "Wi-Fi hotspots."