ont think you can do that without downloading some extra software, but appling permissions will do the same, just instead of typing in a password everytime you want to open the folder, all you have to do is login and out, the default method of doing this is to right or ctrl click on the folder and open get info, the info menu will allow you to lock other users from opening the folders, as long as all the data in the folder is also locked, other users, including admins, will not be able to see the contents of the folder, of course there are ways to get around that but the average user wont be able to as long as you dont leave your account or the admin acount logged in