KB 920342 - PNRP (Peer Name Resolution Protocol) v2 from Vista backported to Windows XP as an update

From what I can tell, this is a protocol much like Rendezvous to discover machines and people that are on your local subnet/etc. I know there is much more involved than that but it looks like a bit of a framework to extend applications like Windows Meeting Place and others.

The best reference I can find about the protocol at the moment is here.

Specifically this section:

Windows Vista includes version 2 of the Peer Name Resolution Protocol (PNRP) that is more scalable and uses less network bandwidth. For PNRP v2 in Windows Vista, Windows Peer-to-Peer Networking applications can access PNRP name publication and resolution functions through a simplified PNRP API. For highly simplified PNRP name resolution in Windows Vista, PNRP names are now integrated into the getaddrinfo() Windows Sockets function. To use PNRP to resolve a name to an IPv6 address, applications can use the getaddrinfo() function to resolve the Fully Qualified Domain Name (FQDN) name.prnp.net, in which name is peer name being resolved. The pnrp.net domain is a reserved domain in Windows Vista for PNRP name resolution. The PNRP v2 protocol is incompatible with the PNRP protocol used by computers running Windows XP. Microsoft is investigating the development and release of an update to the Windows Peer-to-Peer Networking components in Windows XP to support PNRP v2.

It looks like the part that I highlighted in bold finally happened.

You can grab the update for Windows XP here.