China DOS Union

I'm studying computer science at a vocational secondary school. The coursework includes FOXBASE databases, QBASIC, etc. Recently something very infuriating happened: some guy had nothing better to do and, during machine time, randomly deleted other people's files. All the database files in the WYY folder I created are gone. That jerk even thinks he's technically skilled, and goes around bragging that he's a “hacker” — disgusting! Our machines use a DOS system, and they're all connected on a local area network. Please give me an idea how to encrypt or hide my folder (or files). Thanks!