What OS?
You can get a third party utility to create an encrypted disk image and toss your folders in there, and then password protect it. Just remember to never forget your password or use an actual word (to keep it from dictionary attacks), because if you forget the password then your data is gone, but at least its safe.
If you are by slight chance running OS X, this feature is built into the OS.
AES 128bit encryption should do just fine since it would take a super computer a few decades to decrypt that.