Yeah, I'm guessing the aforementioned device does send broadcast packets. What I'm wondering is by what protocol does it do so, why does XP choose to pester my users about it, and how do I kill that kind of traffic on the LAN?

The Karma announces itself over SSDP multicast. If, as a sysadmin, you find yourself needing to filter that traffic, look for UDP packets destined to multicast group 239.255.255.250 on port 1900. That's a "local administrative scope" multicast address, so at least the notifications shouldn't cross routers unless someone's deliberately configured the router otherwise.

Of course, anyone on the wrong side of the filter couldn't then use Rio Music Manager to talk to the Karma: it's only SSDP that lets Rio Music Manager know where the Karmas on the network are.

There's more (lots more) at http://www.upnp.org.

Peter