Lan admin

i have 10 computers in a cyber cafe but they all say that “task manager has been disabled by your administrator…i have tried to make fresh window installations but this happens again after 10mins when i re-plug the network card and worst still am not able to install mcafee antivrus coz it keeps telling me that i have to verify whether i have a enough privileges…! tried editing the registry but everything is is disabled/not configured mode and some computers keep telling me that “registry editing has been disabled by my administrator….am runing nusta dont know what to do NEXT….