VeraCrypt - VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux.
CryptoExpert - Secure data vaults for Windows
Axcrypt - AxCrypt - Password Protect Files With Strong Encryption. AxCrypt is the leading open source file encryption software for Windows.
Renee File Protector - Equipped with AES 256 encryption, Renee File Protector provides overall protection to data in local & external disk. You can lock folders/files at will.
Windows BitLocker - This topic provides a high-level overview of BitLocker, including a list of system requirements, practical applications, and deprecated features.
SSuite Mercury Rising - SSuite Mercury Rising data security software is the best free online AES encryption-based app that runs directly inside your web browser using pure HTML5 and javascript code.