The hidden administrator C$ share that is built into Windows file sharing, can’t be used in Windows 7 or Vista.
The reason this doesn’t work is because of UAC (User Account Control). By default Vista doesn’t allow UAC elevation over the network with a local user account.
There’s a registry key that we can use to change this behaviour.
Manual Registry Hack
Open regedit.exe then navigate down to the following key.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\System
If it doesn’t exist add a new 32-bit DWORD value named LocalAccountTokenFilterPolicy and set the value to 1.
At this point you can map to the C$ share and also perform some other administrative tasks remotely.