I know that on XP pro I could never get the c$ share until I turned off the simple file sharing.
you can do that in my computer>tools>folder options>view tab> and it's at the very bottom. Make sure you have a pass on your admin account if you do let c$ be accessible. You can set an admin password by right clicking my computer and going to manage. Then go to local users and groups>users>administrator. You can rename it and set a password I believe. Also remember that the original account is admin so you should set a password for that too, well I guess it's smart to have a pass for all accounts. and if you don't need to get this stuff from over the internet, block it with a firewall. You can set rules in firewalls to allow over a lan and not from the internet.