Disable Shutdown in Shutdown dialog box.

This is a neat Trick that you can play on your friends. You can disable shutdown option in the shutdown dialog box. This trick involve Registry editing so take the registry backup first.

Launch the Regedit.exe and goto
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer

In the right pane look for NoClose key.
Set its value to 1

doing this disables the Shutdown option in the Shutdown dialog box.
Generally XP and newer version do not give any message.
but older versions give messsage like
"This opoeration has been cancelled due to restriction in effect of this computer. Please contact your system Administrator "


You can re enable the Shutdown option by making NoClose key value eqaul to Zero.