Enable shutdown via ACPI shutdown event/without logging in
Windows Server 2003, by default, won't shutdown on an ACPI shutdown signal.
For a local system, configure: Control Panel → Administrative Tools → Local Security Policy → Local Policies → Security Options → Shutdown: Allow system to be shutdown without having to login.
In Active Directory, to configure: Group Policy Management Editor → Computer Configuration → Policies → Windows Settings → Security Settings → Local Policies → Security Options → Security Options → Shutdown: Allow system to be shutdown without having to login.