That is because you didn't set the Advanced shared settings to "Turn on password protected sharing" and "Turn off public folders..."
The public folders mechanism is less secure and used only when security isn't a big concern... in that configuration only the Public folder is visible to all users, the Lockdown user is most likely visible and accessible because the same user exist on both machines and have access to it.
Please press 
+ R and type fsmgmt.msc
click on Shares and post a screnshoot of this window.
