If you occasionally want to use X window desktop on your PC, you can achieve your goal by one the following two ways.
XDMCP ¶
XDMCP is a protocol implemented by a X display manager, XDM/GDM/KDM.
The protocol allows starting a session on an X server from the local or a remote computer.
First of all, the display manager will start an X server to present user a login form.
So using XDMCP means not only need you run an X server on your windows box, but also you need to run an X server on the *nix box.
The X server on windows machine and display manager on *nix box are using XDMCP protocol to communicate with each other.
Using gdmsetup to set up XDMCP in gnome. Note, you need first to open UDP 177 port on the firewall.
http://en./wiki/XDMCP
Redirect display ¶
By setting DISPLAY environment variable, X clients can delegate display work to a remote X server rather than the local X server. The windows machine running an X server and the *nix box are using X11 protocol to communicate with each other. Please refer to Putty+Xming=Reflection http://www.360doc.com/showWeb/0/8/473778.aspx
The X client used to start gnome desktop is gnome-session.
The X client used to start KDE desktop is startkde.
In /etc/X11/xinit/Xclients you can find the command used to start desktop when type startx
