In Windows 2008, 2008 R2, Vista and Window 7, disabling hibernation via Power Options in the control panel doesn't get rid of the hiberfil.sys file. This file is usually equal to the amount of memory your system has, so it eats up a lot of disk space. This is especially true if you have a lot of memory which is common on servers, or a small amount of disk which is common on virtual machines. To get rid of this file and free disk space, just run the following command from an elevated, or administrative command prompt.
powercfg /h off