Microsoft Knowledge Base Article 920342 contains the following INTRODUCTION:
This article describes an update package that is available for computers that are running Microsoft Windows XP with Service Pack 2 (SP2). This update upgrades Windows Peer Name Resolution Protocol (PNRP) to PNRP version 2.0. PNRP version 2.0 for Windows XP provides the same features as PNRP version 2.0 for Windows Vista.
This update enables Windows XP SP2-based programs that use PNRP to communicate with Windows Vista programs that use PNRP.
Note PNRP version 2.0 is not backward-compatible with earlier versions of PNRP. If you install this update, you cannot use programs that use the updated version of PNRP to communicate with programs that use earlier versions of PNRP. Also, Windows XP does not let applications use the getaddrinfo() Windows Sockets function to resolve PNRP names that are encoded as fully qualified domain names.