How do I enable Network Monitor (Netmon) in Windows Server 2003?
Netmon is part of Windows 2003. To install the tool, perform these steps:
1. Start the Add/Remove Programs Control Panel applet (Start, Settings, Control Panel, Add/Remove Programs).
2. Click the Add/Remove Windows Components button.
3. Select "Management and Monitoring Tools" and click Details.
4. Select "Network Monitor Tools" and click OK.
5. Click Next to proceed with installation. Click Finish, then click Close to exit.

The version of Netmon with Windows 2003 monitors only traffic sent to or from the server. The Microsoft Systems Management Server (SMS) version monitors all packets on the network.
—John Savill