Xming is the leading free unlimited X Window Server for Microsoft Windows (XP/2003/Vista). It is fully featured, light and fast, simple to install and because it is standalone native Microsoft Windows, easily transported portable as a Pocket PC X server. It is totally secure when used with SSH and optionally includes an enhanced PuTTY Link SSH client and a portable PuTTY replacement package.
Xming is cross-compiled on Linux for Microsoft Windows (32-bit x86), using MinGW, mainly from the canonical X.Org source code with my patches applied. It is kept current and secure with frequent updates from X.Org, XKB, FreeType2, Pthreads-Win32 and Freedesktop Bugzilla.
When released Public Domain, Xming can be distributed and used without restriction as it is open source licensed, mostly MIT/X11.