> [...] my ssh session [...]

   On what?

      uname -a
      ssh -V

> export DISPLAY=10.100.4.72:0.0

   Normally, SSH client/server systems can set up X by themselves, so
you wouldn't need to do anything with DISPLAY.  (Was it set before you
started playing with it?)  You may need to specify a command-line option
(like "-x", "-X", ...) to "ssh" to enable this.

      ssh -h

> Xlib: connection to "10.100.4.72:0.0" refused by server

   It sounds as if your X server is not listening.

> The above IP is of my pc, and on my pc I have started xming, but I am
> unable to run it.

   I know approximately nothing about Xming or "my pc", but perhaps
Xming does not normally listen for connections from the outside world.

      http://www.straightrunning.com/XmingNotes/manual.php

Look for "-from".