From Axantum Software:
AxCrypt Portable features easy to use strong file encryption, integrated with Windows Explorer. Encrypt, compress, decrypt, wipe, view and edit with a few mouse clicks. Cryptographic primitives are AES-128 and SHA-1. A combination of strong symmetric encryption with compression and double-click editing/viewing. Encrypted files have a .AXX extension added to their names, and are shown with a new icon. AxCrypt has passed the Microsoft Platform Test for ISV Solutions at VeriTest. Testing was conducted independently by VeriTest, a testing service of Lionbridge Technologies.