Windows XP:- Shut Down Shortcut on Your Desktop:-

If you're trying to eliminate every extraneous mouse click, you can shut down your computer with an icon on the desktop.

1). Right-click on your desktop,
2). click "New," and then click "Shortcut."
3). In the "Type the location of the item" field, type "shutdown -s -t 00"

to give you a way to shut down the computer immediately.

if you want to change shutdown to restart (Change the -s to -r to create a reboot shortcut instead.)