The computers listed in the Network Neighborhood comes from the Browser-list maintained by the computer being Master Browser. A computer can become Master Browser through an election where the computer with the highest prioirty is elected.
There are different roles for computers participating in a Microsoft Network :
Non-Browser: Cannot participate in the election or maintain a Browser-list. Reports to the Master Browser with 12 min. intervals, and presumed dead by the Master Browser if it hasn't reported in 3 intervals.
Potential Browser: Able to be Master Browser if elected and can be chosen as Backup Browser by the Master Browser. Reports back like the Non-Browser and if the Master Browser disappears it can start an election.
Backup Browser: Elected by the Master Browser to mirror the Browser-list. Every 15 min. the Backup Browser requests an updated Browser-List from the Master Browser. There is a Backup browser elected for every 32 computer.
Master Browser: Responsible for maintaining the Browser-list by adding and removing computers for a single subnet.
Domain Master Browser: (Primary Domain Controller) Responsible to maintain the Browser-list in a Domain. It collects Browser-lists from all Master Browsers and distributes the entire Browser-list to all Master Browsers in the domain.
A computer's priority in the election depends on the operating system:
Windows For Workgroups or Windows 9x : 0x01000000
Windows 2000, NT4, XP Prof. : 0x10000000
Windows 2000, NT4 Srv. : 0x20000000
A computer's priority in the election depends on the configuration:
Primary Domain Controller(PDC) : 0x00000080
WINS System : 0x00000020
IsDomainMaster = Yes : 0x00000008
Running Master Browser: 0x00000004
MaintainServerList = Yes : 0x00000002
Running Backup Browser: 0x00000001
Note if a computer is frequently turned On/Off or having few resources available(Mobile Computer), then one should configure it as Non-Browser so it won't start unnecessary elections.
Note if having a LAN where one computer is configured to belong on a different subnet than the default or if the computer for some other reason cannot see the current master browser (Usually the Primary Domain Controller). Then this computer will constantly issue Master Browser election, because it cannot find a Master Browser. This can lead to a blank Browser-list for all the computers in the LAN.
Note if a router is used to connect two LANs and it is configured wrong, then the two LANs will affect each other in the Master Browser election. This can lead to a blank Browser-list for all computers in both LANs.
One can control how a computer participate in the Master Browser election, with these STRING registry keys :
[HKEY_LOCAL_MACHINE \System \CurrentControlSet \Services \Browser \Parameters]
MaintainServerList = "Auto" (Pro = "Auto", Server = "Yes", Off = "No"

IsDomainMaster = "True" (On = "True", Off = "False", Default = "False"
The MaintainServerList controls if it should participate in the election at all.
The IsDomainMaster gives the computer a higher priority in the election.
Note to discover/detect the current master browser on the network use the reskit tools browmon or browstat.
Note if the service Computer Browser is disabled then the computer will not participate in the election. Setting MaintainServerList = No will keep the Browser service from starting, any attempt will give the following error:
A service specific error occurred: 2550.
One can control how a computer participate in the Master Browser election, with these STRING registry keys :
[HKEY_LOCAL_MACHINE \System \CurrentControlSet \Services \Browser \Parameters]
MaintainServerList = "Auto" (Pro = "Auto", Server = "Yes", Off = "No"

IsDomainMaster = "True" (On = "True", Off = "False", Default = "False"
The MaintainServerList controls if it should participate in the election at all.
The IsDomainMaster gives the computer a higher priority in the election.
Note to discover/detect the current master browser on the network use the reskit tools browmon or browstat.
Note if the service Computer Browser is disabled then the computer will not participate in the election. Setting MaintainServerList = No will keep the Browser service from starting, any attempt will give the following error:
A service specific error occurred: 2550.
One can control how a computer participate in the Master Browser election, with these STRING registry keys :
[HKEY_LOCAL_MACHINE \System \CurrentControlSet \Services \Browser \Parameters]
MaintainServerList = "Auto" (Pro = "Auto", Server = "Yes", Off = "No"

IsDomainMaster = "True" (On = "True", Off = "False", Default = "False"
The MaintainServerList controls if it should participate in the election at all.
The IsDomainMaster gives the computer a higher priority in the election.
Note to discover/detect the current master browser on the network use the reskit tools browmon or browstat.
Note if the service Computer Browser is disabled then the computer will not participate in the election. Setting MaintainServerList = No will keep the Browser service from starting, any attempt will give the following error:
A service specific error occurred: 2550.
If the Computer Browser service is stopped on a Workgroup workstation, you can still access and share files, through direct UNC paths or persistant paths from previous sessions, but you will likely no longer be able to browse through Network Neighborhood.
References: