[Gizmo]

The Computer Browser service maintains the list of servers in a workgroup or domain.

For a domain, the domain controller and backup DCs are responsible for maintaining the Master Browse List. They will elect other servers, and then workstations which run the browse service, to maintain copies as well, based on the number of machines on the network and what network segments they are on (each network segment will typically get at least one Browse Master).

For workgroups, the situation gets a bit more complicated, because there is no Domain Controller. Basically, when a machine running the Computer Browser Service starts up, it forces an election on the network. Servers win over Workstations, Newer OS versions win over older OS versions, and machines with longer uptimes win over machines with shorter ones.

So, when you get that message, it means that there is no machine on the network which is a member of that workgroup and is running the Computer Browser Service, which is a Browse Master, and can be contacted by the machine you are running from.