Running Ubuntu within Windows

Running Ubuntu within Windows

Basically I have a couple of C# apps running on Windows Server and I want
my webserver to communicate with them securely locally, I have setup
Ubuntu Server 64bit with VirtualBox, how can I make the Ubuntu server
respond instead of the Windows WNMP?
I want to be able to send packet to localhost and receive them in Windows
from the Ubuntu webserver running on Virtual Box, when a user visits my
webpage I want the Ubuntu webserver to handle the request. The Windows
Server 2012 is out of the box install and Ubuntu Server 12.04.2 LTS is as
well, latest VirtualBox is running too. I can specify a different IP
within the local network in the PHP WNMP files so I am curious if I can
get it to work like that. What other details should I provide?