If your Shutdown Command is Disable:

Shutdown Command - Disable Follow these steps to recover it back :

1. Follow this path : Start>>Run>>GPEDIT.MSC

2. Now go to :

Computer Configurations/Windows Settings/Security Settings/Local Policies/User Rights Assignment/Shut Down the System/Users/Remove.

There may be certain machines that you do not want to be shut down; for instance, a workgroup print server, or a machine in
a kiosk.

With this Registry edit, you can take away that option:

Follow this path : Start>>Run>>regedit

Hive: HKEY_CURRENT_USER
Key: \Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Name: NoClose
Data Type: REG_DWORD
Value: 1

Done!

Enjoy,

Admin.