|I've never been able to access a drive or a directory that wasn't shared. A shared drive or directory has the hand icon under it. If that icon isn't there, the folder is already private. If for some reason it isn't working that way, continue reading.|
Is file & printer sharing checked in the properties of LAN, under network, in the control panel? Unchecking that stops all sharing.
If you want to password protect each PC, you run lusrmgr.msc, go to the user folder, right click on the user name, then click set password. After that, go to user accounts in the control panel. Choose change the way users log on or off. Check that they have to enter a password instead of using the welcome screen.
That will ask for a password at boot time & ask for a password if the PC is accessed remotely.
How do you know when a politician is lying? His mouth is moving.