By default, if you delete the C$, D$, etc.. Administrative shares, they will be recreated when you reboot. To disable this feature, edit:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\LanmanServer\Parameters

Double click on AutoShareServer and set it to 0 to disable it for a server.
Double click on AutoShareWks and set it to 0 to disable it for a workstation.
If the entries are not present, Add Value of type REG_DWORD. The Range is 0 (disable) or 1 (enable - the default).