Question : Can't see all the XP systems on my network in workgroup

I am trying to setup some networking and I can't see all the XP
systems in the workgroup.
But, the systems that I can't see are in another room. Different
subnet, different switch.

What ports should I verify that are open to allow the system to access
each other ?

Answer : Can't see all the XP systems on my network in workgroup

Set master Browser:

Open regedit
Goto HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser\Parameters
Set IsDomainMaster to TRUE

Install WINS
http://technet2.microsoft.com/windowsserver/en/library/702d3b5d-91be-40ed-a7e2-cf35ac978e191033.mspx?mfr=true

Then make sure and point all workstations to that server for WINS under the  network settings