Windows XP includes a command called Shutdown that does much more than its name might suggest. Yes, you can use it to create a shortcut that you can then double-click to turn off your computer instantly. Just create a new shortcut and include this command in it, exactly as typed:
shutdown -s -t 00
The -s switch means “shut down” (you could use -r to shut down and restart). The -t switch defines a waiting time, measured in seconds.
You can also use the command to do other tasks, such as logging off the current user (use the -l switch), or restarting a remote computer on your network (with the -m switch followed by \computername) . Using the -i switch, you can show a graphical user interface (normally, this is a text-based command). You can include the shutdown command as the last line of a batch file or script to restart a computer after performing a maintenance task.
To see the full syntax for the Shutdown command, open a Command Prompt window (Start, Run, type cmd and click OK) and type the command shutdown without any additional switches or arguments.