if you use windows XP and bring up the Task manager you can shut it down that way but you can not shutdown the comp via the start menu. If you use VNC you can get it to shutdown via the start menu. basically you will need some sort of Remote Control software the the computer you want to shutdown.
if you fire up MMC (microsoft management console), and snap-in the computer management, then you can shut it down by:
a) connect to forign machine (must know username/password of someone with permission), by right-clicking "Computer Management (Local)" and selecting "connect to another computer".
b) right click "Computer Management (Forign Machine)" properties.
d) Startup & Recovery
e) Shutdown button
f) choose what you want to do: Log off user, Shut down, Restart, Powerdown, and you can force apps to close.
start -> run -> mmc
start -> settings -> control panel -> administrative tools (XP-in classic view) -> computer management
start -> programs -> administrative tools -> computer management
(to get this one, right click on your taskbar/properties/advanced, and check the box beside "display administrative tools")