Xming is the leading X Window System Server for Microsoft Windows®. It is fully featured, lean, fast, simple to install and because it is standalone native Windows, easily made portable (not needing a machine-specific installation or access to the Windows registry).
There are two releases of Xming, the public domain release is free but the version is slightly older. The web site release can be accessed for a small donation.
The public domain release is avaialble at https://sourceforge.net/projects/xming/. The web site release can be found at http://www.straightrunning.com/candidate/PLEASE-READ.