Xming is the leading
X Window Server for Microsoft
XP/2008/Windows7. It is a fully featured X Server and is lean, fast, current, simple to
install and because it is standalone native Microsoft Windows®, easily made portable (not needing a machine-specific installation).
Xming is totally secure when used with
SSH and optionally includes an enhanced
PuTTY Link SSH client and a
portable PuTTY replacement package. Xming can work completely independent of the Window's registry when used with
Xming-portablePuTTY.
http://www.ece.uvic.ca/computing/win-xsessions.shtml