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

[ksc133]

hello everybody,

i have 1 problem with samba NT styled domain logon.
when i logon as root into a win2k box, i can connect and disconnect to 
domain, shutdown the PC and do many other stuff. cos i list domain admin 
group  = root in my smb.conf file.

but when i logon as other users, i can't even shutdown the win2k box!!!
i don't want to list all my users as domain admin group.
i try using the domain user group, but still the same problem, can't 
shutdown.
how to over come this problem???
i didn't use any system edit program on the win2k box to restrict any 
users, but why users become restricted??? can't even shutdown PC???

pls help me thanks!