user accounts and keeping files secure


I have windows XP home and am computer administrator on the user accounts. I have a son who has his own account, and is limited user.

I was under the impression that he could not see or access MY folders, unless I specifically "shared" them. However, when I looked on his screen I was able to open my private files, yet they are not ticked for sharing.

Am I missing something here, any advice please. I am happy for him to share certain folders etc, but not all my private folders.

Thank you