SecurStick - Free portable application that lets you carry encrypted files on your USB drive.
VeraCrypt - VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux.
Axcrypt - AxCrypt - Password Protect Files With Strong Encryption. AxCrypt is the leading open source file encryption software for Windows.
Microsoft BitLocker - BitLocker is a full disk encryption feature included with Windows Vista and later.
Windows BitLocker - This topic provides a high-level overview of BitLocker, including a list of system requirements, practical applications, and deprecated features.
Symantec Data Loss Prevention - Fully protect your data with the comprehensive detection technologies and unified policies of Symantec's industry leading Data Loss Prevention (DLP).