From Estelar Software Group:
Estelar Lock A Folder is a lightweight and easy to use window security program which you can use to lock a folder, file and other computer resources to make them inaccessible to both local and remote users. If you share your computer with others like your colleagues, family or friends, you can use this tool to completely hide your folders and files until a valid password is entered.
It is a reliable and easy to use tool to lock a folder or file. It Is designed to password protect files and folders from being seen, read or modified by unwanted users. You can even disable access to the floppy, CD-ROM and other removable drives connected to your computer. Once you lock a folder of file with this tool, it cannot be seen or accessed without running the Lock A Folder and knowing the right password. Thus, renaming the locked folder, accessing them using DOS, booting to Safe Mode, reinstalling windows to recover hidden folder or files will not make locked files and folders accessible at all.
Just 4 simple steps and your folder or file will be completely secured from unauthorized or unwanted access in no time. The program will not hamper or damage your folders or files during or after the encryption, in any way. It supports both NTFS and FAT/FAT32 drives.