This will add / remove the shutdown button at the
first logon dialog.When you say this comes handy then
follow the path below :


- HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
\CurrentVersion\policies\system\


Create here in the right pane a new entry called :


ShutdownWithoutLogon


(create : right click , new , REG_DWORD [DWord Value] and name it as above)


Doubleclick this entry and set it's value to 1 to display
the button.0 will remove the button.

Restart your computer and see the effect at the logon screen!