This task will also work when you have the proper rights to access this share. The C$, D$, etc. admin shares requires admin privs to access them. There are a couple of options you have to make this work:
1. Prior to executing this task, map a network drive from that machine with a user account which is at least local administrator on the remote machine.
2. Use the task to start a batch file which establishes the connection (you could even pass username, domain and password to that batch file from your connection settings)
3. Use PSEXEC (as demonstrated in other posts in the toolbox forum) to start a process with a user that has at least local admin rights on the remote machine.
cheers
Stefan