Este post, dos fóruns da Technet, de Yan Li explica isso com bastante facilidade:
Only the Administrators group have access to the administrative shares, please go to the Administrators group and remove the desired users and groups that you do not what to have access to the administrative shares.
For multiple client PCs, you could on one of the machines and disable them as stated below, export the registry key and then in a GPO import it.
Disable the default shares:
Windows open hidden shares on each installation for use by the system account. (Tip: You can view all of the shared folders on your computer by typing NET SHARE from a command prompt.) You can disable the default Administrative shares two ways.
One is to stop or disable the Server service, which removes the ability to share folders on your computer. (However, you can still access shared folders on other computers.) When you disable the Server service (via Control Panel > Administration Tools > Services), be sure to click Manual or Disabled or else the service will start the next time the computer is restarted.
The other way is via the Registry by editing HKeyLocal Machine\SYSTEM\CurrentControlSet\Services\LanManServer\Parameters. For Servers edit AutoShareServer with a REG_DWORD Value of 0. For Workstations, the edit AutoShareWks. Keep in mind that disabling these shares provide an extra measure of security, but may cause problems with applications. Test your changes in a lab before disabling these in a production environment. The default hidden shares are:
Share:
C$ D$ E$
Path and function:
Root of each partition, only members of the Administrators or Backup Operators group can connect to these shared folders. For a Windows 2000 Server computer, members of the Server Operators group can also connect to these shared folders.
Ainda assim, não é uma boa prática fazer isso. Você está impedindo o acesso a coisas que devem estar acessíveis para um administrador de domínio. É como mudar as fechaduras do seu apartamento para que o seu senhorio não possa entrar.