How to shutdown and reboot computer from remote desktop / session?

I need to shutdown remote computer after use it.

I can disconnect the user but computer is still running. How to I shutdown ?
Also
Sometimes I need to restart my remote computer when I am using it through remote desktop . How can I do that ? My remote computer is windows XP.

nice.. thanks

While you are connected over Remote desktop in windows xp

Goto --> Start --> windows security --> Shutdown --> Turn OFF .

Done.. there is also option to reboot.