Any popular, open-source, and/or portable application that prevents users from opening a folder or a program by requiring passwords? For strong privacy and security, I would encrypt my files with something like TrueCrypt. However, I want a quick way to access files by just entering a password in order to access a folder or a program after double-clicking the file. I know that it's not necessary as secure as encrypting the files, but it would be far more convenient. This allows me to let my friends/family use my computer without them tinkering with private data--they can do the basics like general web browsing or playing a video from their hard drive.
I've googled and found some several programs to fulfill this need, but they are all very obscure and unpopular programs made by someone who had some free time on their hands.
I can create a limited account on Windows for this purpose, but it takes up unnecessary space, time, and resources, and I want to maintain certain settings that I have on my primary account.