Shutting down a Ubuntu server remotely from Windows?

[Tom Schinckel]

Okay, so I've turned an old box into a Ubuntu file server for the old 
man to keep his dodgey 80's music and other "important" files of his 
which he can access via Samba etc. on his XP desktop. Anyway, the 
problem I'm having is that he doesn't want it running 24-7, thus I'd 
like a way of remotely turning the thing off. Currently, the only way to 
do it is too ssh in and go sudo shutdown -P now, but that's a bit 
complicated for him, so he'd prefer if he could just click an icon on 
the desktop or something. I'm not to concerned if it's insecure, because 
everything's sitting behind a firewall.

Any ideas?