Windows Page File
Space in the page file (without neccessarily ever being written to) is required for a number of things. e.g. allocating a memory mapped file that is backed by the page file (which is what is commonly refered to as "shared memory") reserves space in the page file. If there is no page file a number of things in windows stop working, dependently if data actually ever ends up being written into the page file or not.
Turning the page file off completely under windows is a no-go. It will create issues in many programs.