[Samba] user can't shut down windows clients?

[ksc133]

dear sir,

i have create a few users of the nobody group on my samba server.
in my samba config, i listed root account as the domain admin group.
when i logon to samba server, my root account can shutdown my windows 
client, can disconnect to domain ect etc...
but when i logon as a user of the nobody group. i can't shutdown the 
windows client! the shutdown fucntion is not there anymore!
i don't want to list restricted my users as domain admin group.
is there any way to get around is problem?
thank Q!