How to remote shutdown a win XP machine from linux?
Does the psshutdown tool from SysInternals (nor part of MS) work under Wine? Probably not, but might be worth a try.
Failing that you could install cygwin's OpenSSH port (or some other SSH server service) and use that to login and call Windows' own local shutdown command - this would be a one line command/script.
psshutdown doesn't work from wine for some reason.
however,
net rpc shutdown -I xxx.xxx.xxx.xxx -U username%password
works if all the proper steps have been taken