06-30-2009 04:20 PM
Welcome to the Lenovo forum
If you press F1 at boot to get to BIOS Setup, then go to the Config: Beep and Alarm section, there's a setting for "Power Control Beep". Try setting that to "Disabled".
If the above doesn't work, have a look at the settings available in Power Manager, available by pressing Fn-F3 from Windows.