Free Windows system disk space by disabling hibernation
If you don't use 'hibernation' mode for you computer, you can free up a large amount of system disk space by completely disabling hibernation. This will remove the very large, hidden system file hiberfil.sys from your system partition.
The only sure fire method of disabling Hibernatation in Windows 7 and removing the hiberfil.sys is through the command prompt:
1) Open a command prompt with administrative privileges
2) Enter “powercfg.exe -h off”
3) Exit the command prompt
4) Reboot the machine