With Central Management Servers  (SQL 2008) you can run this script against all instances in your environment to give you a list of all servers and their fixed ports (NULL if no fixed port).

setnocounton

DECLARE @port varchar(20), @key varchar(100)

begin

set @key ='SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL.1\MSSQLServer\SuperSocketNetLib\Tcp\IPAll'

end

EXECmaster..xp_regread@rootkey='HKEY_LOCAL_MACHINE',

@key=@key,@value_name='Tcpport',@value=@port OUTPUT

SELECTCAST(SERVERPROPERTY('MACHINENAME')ASVARCHAR(128))asServer Name,

@@servicenameas Instance,

@port as port