Windows 8 increased the boot speed by making use of the hibernate function to store the kernel session rather then completely shutdown.
For laptops and even desktops; this is a nice feature. However, for a testing server or virtual machine; this is a waste of disk space especially if you have a large amount of RAM (in one situation, a windows 7 and 8 setup had two sixty gig files for hiberfil.sys).
This consumption also confused the users as they would see their free space as small and yet looking at their folders didn’t show these files. Programs like windirstat will point this out.
The simplest way to disable this feature is to use the powercfg command. Start an administrative level cmd shell.
Enter: powercfg /h off
The hiberfil.sys file will disappear right after.
Startup time will increase but for these users; space was more important.