These commands can be used either from the Windows XP Command Prompt or in a bat command file
To Shutdown your Computer
shutdown -s
To Shutdown and Restart your Computer
shutdown -r
To Shutdown or Restart but delay the command
use the -t nnn minutes option where nnn is the time in minutes
e.g shutdown -r -t 60
This will restart your computer in 60 minutes
To Lock your computer
Rundll32.exe User32.dll,LockWorkStation