From Microsoft:
http://support.microsoft.com/kb/922120
SYMPTOMS When you run Network Map on a Windows Vista-based computer, computers that are running Windows XP do not appear on the network diagram. Note This article describes an update that will make 32-bit Windows XP-based computers appear in Network Map on Windows Vista-based computers. For more information about how to set up or to troubleshoot networking between Windows Vista and Windows XP, see the "More Information" section.
CAUSE This problem occurs if the Link-Layer Topology Discovery (LLTD) Responder component is not installed on the Windows XP-based computer. Network Map in Windows Vista makes network diagrams of the connections between network devices that can be used to troubleshoot connectivity problems. Network Map uses a discovery protocol called Link-Layer Topology Discovery (LLTD) that queries other devices on the network to determine how the network is organized. Windows Vista includes the software components that implement the LLTD protocol. For other devices on the network to be displayed on the map, they must enable a discovery protocol that can respond to the mapping requests from the Windows Vista-based computer.
Network discovery needs to be turned on on the Vista-based main computer as well.
We don’t have Vista.
The real problem started when the stray got his hands on the computer. The system worked fine for two weeks.
I’ll take another look at it tonight.
I’ll reread all of y’all’s post too.