By default, "Everyone" has NO ACCESS to the root of C.
What you have done is to create a share, pointing to the root of C, to which Everyone has no access.
You would also need to allow Everyone (or else each explicit user) at least Read and List NTFS rights to make this work - although it is very poor security to do so, as Mac has already pointed out.
Of course, you can always Map a drive to the root of C on the other system using the c$ admin share - you then need to Logon As and supply an account with admin rights on the target PC: PCName\Username.
SD