[CentOS] Turning off Win2008 machines from a CentOS box

I understand this may be able to be done with Samba?
Anyone know the syntax for a CentOS 5.1 Samba client
and what needs to be done to Windows 2008 Server to
allow this (I suspect out of the box it wouldn't allow it)?

I was hoping to use SSH with keys and script the login
and execution of the native win shutdown command, but
I have had troubles making any of the usual win SSH
Daemons work under Windows 2008 Server x64.

Any ideas would be appreciated!
jlc