Lifehacker reviewed a utility that makes encryption a piece of cake: EncryptOnClick.

“Windows only: Have you ever wanted to lock down a few files behind passwords, but don't want to jump into a full-featured encryption system with multiple keys, virtual drives and whatnot? Free encryption utility EncryptOnClick is a dead-simple utility that gets the job done. Open the program, choose a file or folder to secure, and type in your password. The files or folder will get an encrypted icon, and you'll be asked for the password to open them—and that's it, at least with the freeware version. The app uses 256-bit AES encryption, so for hiding stuff from the average snooper, it's a tight and light solution. EncryptOnClick is a free download for Windows systems only.”