Before we look at how to go about deleting the hiberfil.sys file on your Windows PC, it would be prudent to explain what the file is.
hiberfil.sys is the Windows system file located in C:/hiberfil.sys that is responsible for enabling hibernation to function on you computer, by writing the computer’s memory (RAM) out to your hard drive, storing the current state of your computer before powering down. The size of the hiberfil.sys will depend on how much RAM your system has installed. For example, I have 16GB of RAM installed on my Windows 7 machine, so the hiberfil.sys file will be approximately (12.5GB currently) the same size. By default, hibernation is set to the On state in Windows and can be a very useful function and speed up the time it takes waking up from hibernation. However, if you never use the hibernation function in Windows, or have space limitation worries and would like to delete this file, then you are able to do so safely. you will have to show hidden files and folders (via folder options in your Control Panel) to be able to see this file as it is hidden by default.
Note: Windows 8 users should not do this as the hibernation function in Windows 8 and 8.1 is responsible for the fast boot times that Windows 8 users enjoy. You can still do so if you feel you really need to.
For Windows XP this is pretty simple to do.
Head to your Control Panel (switch to Classic View) and locate the Power Options. (Start>Control Panel>Power options) In the Power Options Property window that opens, select the Hibernate tab and uncheck Enable Hibernation. (as shown in the image below) Now reboot and the hiberfil.sys file should be gone and you will have freed up some space on your HDD/SSD. If you still see it there, feel free to just delete the file in C:/hiberfil.sys.
Note to re-enable hibernation, simply re-check the box again.
For Vista and Windows 7 users, you will have open the Command Prompt at an elevated level. To do this, click Start and type cmd into the search box. Right-click on cmd.exe and select Run as administrator
type in the following command and the prompt followed by Enter to execute it.
powercfg -h off
That’s all there is to it. If you wish to re-enable it in the future then simply type the same command at an elevated command prompt but swap off for on