This is a visual diagram of how computer discovery works in OpsMgr 2007. The list of prerequisites required to discover servers and install an agents are listed below as well:
Description: RPC endpoint mapper
Port number: 135
Protocol: TCP/UDP
Description: NetBIOS name service
Port number: 137
Protocol: TCP/UDP
Description: NetBIOS session service
Port number: 139
Protocol: TCP/UDP
Description: SMB over IP
Port number: 445
Protocol: TCP
Display Name: Netlogon
Started: True
State: Running
Description: MOM Channel
Port number: 5723
Protocol: TCP/UDP
Display Name: Windows Installer
Started: True
State: Running
Enable: File and Print Sharing
Steps on how to enable F&P can be found here: http://technet2.microsoft.com/windowsserver/en/library/0cf7e1a7-f7a2-49f9-8fee-730d9d1ea2071033...
Enable: Remote Administration Exception
Steps on how to enable Remote Admin can be found here: http://technet2.microsoft.com/windowsserver/en/library/b8057a7a-a0d3-40b5-8224-ea6a4f5e17231033...
Satya Vel