C$, D$ et all are 'administrative shares' which are special purpose shares and which are under certain limitations, especially under newer versions of Windows (Vista and up). It's pretty bad practive to use them for general file sharing access. They should really be left alone.
Instead of using the administrative shares, you should set up a proper share, i.e. creating a folder, setting up share and proper access privileges for an unprivileged user, and then refer to it by it's share name, i.e. \\mypc\shared_folder or \\192.168.0.1\shared_folder.