If you ever try to stop sharing ADMIN$ (C:\Windows) you find yourself seeing that this same share is available after restart.
To permanently disable administrative shares:
ADMIN$ (C:\Windows)
C$ (C:\)
You need to edit Registry
For NT 4.0/W2K/Windows Server 2003s
HKLM\SYSTEM\CurrentControlSet\Services\LanManServer\Parameters
Name: AutoShareServer
Data Type: REG_DWORD
Value: 0
For NT 4.0 Workstation/W2K Pro/XP Pro
HKLM\SYSTEM\CurrentControlSet\Services\LanManServer\Parameters
Name: AutoShareWks
Data Type: REG_DWORD
Value: 0
If you can't find the value in the registry under the exact location, value must be created
right click in the right pane of the window > New > DWORD Value
Some applications depend on the presence of these shares
To re-enable the shares simply change value to 1