AxCrypt

AxCrypt is free and easy to use open source strong file encryption for Windows 95/98/ME/NT/2K/XP, integrated with Windows Explorer. Encrypt, compress, decrypt, wipe, view and edit with a few mouse clicks. Cryptographic primitives are AES-128 and SHA-1.

Features

The following are features that really set it apart from all other file encryption tools, commercial as well as free:

Double-click to edit/view with any application.
Automatic re-encryption after modification.
Absolutely no user configuration necessary or possible before use.
Open source under GNU General Public License.
7 languages in one executable distribution.
Extensive command-line interface for scripting and programming.

Other features

Windows 95/98/ME/NT/2K/XP compatible.
AES encryption with 128-bit keys.
Edit an encrypted document directly with double-click.
Optional pass phrase cache - type pass phrases once per logon and/or reboot.
Automatic pass phrase validation before decryption or editing.
Key-File generation and support.
No options or user interface - easy to install and use.
Relatively light-weight, less than 1Mb download
Extensive command-line interface.
Server mode options.
Huge file support > 4GB (on Windows NT/2K/XP).
Dynamic brute force counter measure - iterative key wrapping.
Integrates well with web based file sharing services.
Selective compression before encryption - faster downloads/uploads.
Retains original file name and information of an encrypted file.
Integrated shredder.
Shredding of all temporary and encrypted plaintext files.
Secure memory handling - no keys or data in the paging file.
Industry standard algorithms.
Data integrity verification - no undetected modification.
Unique data encryption keys used for every file and (re-)encryption.
Polyglot - currently speaks English, German, French, Spanish, Italian, Hungarian and Swedish.
Easy to add more languages - contact me (I'm especially looking for Nordic languages)!
Open source - no backdoors.
Private branding support for commercial or corporate versions.
It's FREE!