X forwarding from Ubuntu Server Ed to Windows 7
To forward X11 apps over your ssh connection, there needs to be something on your Windows client to which the X11 applications can connect. In other words, you need to run an X server for Windows, which will translate X11 protocol messages from the ssh connection into graphical drawing commands and send mouse and keyboard actions back across the network.
There are several options for this, one is Cygwin/X: http://x.cygwin.com/