Here you go.

http://www.softpedia.com/get/Security/Lock...der-Hider.shtml


This is what I gave my dad when he ran across the same problem with my 17 yr old stepson finding his porn on his laptop. He has been using this and loves it. Just remember to use a strong password. (8+ characters with caps, numbers and special char's) or they will find a way to brute force it in hours if you are away.
(the're are pw crackers for everything these days)
The downside is that it is shareware, and costs $30 to purchase, but for sanity, $30 is worth it to some people. (my dad included)

here's the description from softpedia:


AB Folder Hider description

AB Folder Hider is a powerful hide folder software that can password lock your personal files and folders.
You can use AB Folder Hider to stop other users from opening your personal files, or you can completely hide your files until a password is entered.
It is very useful to keep your personal files away from others.
It is also a powerful guard folder or hide folder software.
AB Folder Hider can lock folders and files in a flash.
It is very useful to keep your sensitive files away from others. It makes your files unaccessible and undeletable.
It is also a powerful folder guard software.
AB Folder Hider works on all 32-bit windows such as Windows 95/98/Me/2000/NT/XP.
AB Folder Hider is very easy to use, everyone can master it in 5 minutes.