prevent access to other files

I have WIN2k Advanced Server Domain and about 50 clients
and each user has a user account to use it to log on the
domain
,the major of the users' accounts are power users (with
respect to their pcs)
but some of them are local administrators (with respect
to their pcs)
and both of them are just normal domain users with
respect to the domain active directory
they are normal users
the problem is:-any user who has a local administrator
account could access any data located on any hard drives
of other pcs connected to the network except the servers
and I Want to prevent the local administrator to do so




I tried More And More But No result.
Help will be so much appreciated

Best Regards:-
Ahmed Nour