Go to Control Panel, Administrative Tools, Services and stop Windows Time. Then turn it to manual, or disable it. Every time your system clock gets synchronised with a time internet server, port 123 will open up. Upon reboot it should be closed again.
Of course, if Windows Time service is disabled it will not open up and you won't be able to synchronise your system clock.
Running "netstat -an" on a command prompt will show you whether port 123 is open or closed. -- Regards, Mick