This is a strange one, I was trying to figure out why a Windows 2008 Server seemed to have no HardDisk space. Upon using Free Tree Size 

http://download.cnet.com/3001-2248_4-81064.html?spi=ccd77cf4907d14695d80119f56be7ff6

I found out that there is this file called " hyberfil.sys", which is a hibernation file that grows tot he same size as your RAM footprint, IE 8GB RAM 8 GB file. 

powercfg.exe -h off, worked for me disabling hibernation, should be done if you have a battery back up only.

or

powercfg.exe /h off

http://connect.microsoft.com/WindowsServerFeedback/feedback/details/335940/disable-hibernation-on-windows-server-2008-by-default