There are generally two reasons why you may want to disable access to the Shut Down command. If the computer is one that should rarely be shut down, such as a kiosk, you should disable access to the Shut Down command. Secondly, by using the Shut Down command, a user can get access to the Boot menu and make unwanted changes. If you are concerned about any users accessing the Boot menu, you should disable access to the Shut Down command.

To prevent users from accessing the Shut Down command in Vista:

1. Open the Group Policy Editor.
2. Navigate to User Configuration / Administrative Templates / Start Menu & TaskBar.
3. In the details pane, enable the Remove and Prevent Access to the Shut Down Command policy option.
4. Restart your computer or type gpupdate /force at the command prompt.