Administrative Templates\Start Menu and Taskbar\Remove and prevent access to
the Shut Down command
[[Prevents users from shutting down or restarting Windows. This setting
removes the Shut Down option from the Start menu and disables the Shut Down
button on the Windows Security dialog box, which appears when you press
CTRL+ALT+DEL. This setting prevents users from using the Windows user
interface to shut down the system, although it does not prevent them from
running programs that shut down Windows. If you disable this setting or do
not configure it, the Shut Down menu option appears, and the Shut Down
button is enabled. Note: It is a requirement for third-party applications
with Windows 2000 or later certification to adhere to this setting.]]
from...
Remove and prevent access to the Shut Down command
http://www.boyce.us/gp/gpcontent.asp?ID=352

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Hope this helps. Let us know.
Wes
MS-MVP Windows Shell/User
> I just migrated several PCs running Windows XP Pro SP1 from a Windows NT
> 4.0 domain to a Windows Server 2003 domain running AD. The user profiles
[quoted text clipped - 4 lines]
> Any idea what would cause this behavior or how to fix it? Thanks in
> advance.