This policy setting turns off the Windows Startup sound and prevents its customization in the Sound item of Control Panel.The Microsoft Windows Startup sound is heard during system startup and cold startup and can be turned on or off in the Sound item of Control Panel.Enabling or disabling this setting automatically prevents users from customizing the default behavior of the Windows Startup sound.If you enable this policy setting the Windows Startup sound is turned off for all users.If you disable this policy setting the Windows Startup sound is turned on for all users.If you do not configure this policy setting the Windows Startup sound is turned on for all users by default and is customizable in the Sound item of Control Panel.This policy setting does not prevent users from setting preferences for other system sounds.
System\Logon
Machine
At least Windows Vista
HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System!DisableStartupSound
Logon.admx