One of the things I found out when using Spacesniffer was that there existed a big hidden file on my Windows Server 2008 system drive called hiberfil.sys. Apparently when you hibernate your computer, Windows saves the contents of the system's memory to the hiberfil.sys file. As a result, the size of the file is as big as the amount of physical memory present. Since I allocated 6 GB RAM to my virtual Windows Server 2008 – the file was a whopping 6GB big ….
Now to remove it – open command prompt (remember to use the run as administrator option) and type powercfg.exe /h off.
For some background info check out KB920730 – How to disable and re-enable hibernation on a computer that is running Windows Vista.