Okay my question is that, I want to run a heavy application, on a Virtual Machine (VirtualBox) with just 2 GB RAM (Windows 7 32Bit Host has 4 GB, 3.5 GB effective). Initially I thought of installing Ubuntu Server 12.04.1, which doesn't come with a GUI, so I thought it would be efficient in performance, but I have only Ubuntu 12.04 Desktop.

My question is, is it possible to remove the GUI parts in Ubuntu 12.04 Desktop (Not Server), keeping only the core OS, after installation in a virtual machine? 

Or, is there anyway to improve the performance of the OS?

If you need more information, I am ready to provide.

I don't want the GUI or anything, even a small terminal window is fine for me, I can access files through FTP.