GPG4Win

Gpg4win enables users to securely transport emails and files with the help of encryption and digital signatures. Encryption protects the contents against an unwanted party reading it.
Digital signatures make sure that it was not modified and comes from a specific sender.

Gpg4win supports both relevant cryptography standards, OpenPGP and S/MIME (X.509), and is the official GnuPG distribution for Windows. It is maintained by the developers of GnuPG.

Gpg4win Components

Gpg4win is an installer for Windows and contains several Free Software components:

GnuPG
The core; this is the actual encryption tool.

Kleopatra
A certificate manager for OpenPGP and X.509 (S/MIME) and common crypto dialogs.

GPA
An alternative certificate manager for OpenPGP and X.509 (S/MIME).

GpgOL
A plugin for Microsoft Outlook 2003/2007/2010/2013 (email encryption).

GpgEX
A plugin for Microsoft Explorer (file encryption).

Claws Mail
A complete email application with crypto support.

Gpg4win Compendium
The documentation (for beginner and advanced users), available in English and German.