How do I password protect a folder on a USB or external hard drive so that no one can view it on their PC?

If you have a hidden folder (using ANY software), once you copy it to your USB or an external hard drive, it seems anyone can just grab it and walk it over to their PC and view all your files (since it's no longer protected). I need a free and SIMPLE way other than something like truecrypt. Obviously, the windows folder hiding option doesn't work (plus I want to be able to see the folders but have them password-protected only). Also Winzip doesn't work since you can encrypt it with a password but then all they have to do is mouseover the folder and it pretty much shows a lot of the contents. So, prefer a software or utility that you can install ON the USB / external HDD itself and allow password-protection of specific folders instead of the entire drive. Thx