re: I wanna hide it!
Depending on what system you are using (Mac, PC), the first step would be to create a new user environment for your kids, and keep yours isolated by password. Users in Windows can be modified to place them in one of several groups, with varying powers to alter the computer.
You can do similar things on the new Mac OSX. The barriers between users are quite robust, and other users can't even write to folders or hard drives that belong to the primary user.