Windows has two power management modes that you can choose from: one is Sleep Mode, which keeps the PC running in a low power state so you can almost instantly get back to what you were working on. The other is Hibernate mode, which completely writes the memory out to the hard drive, and then powers the PC down entirely, so you can even take the battery out, put it back in, start back up, and be right back where you were.
Hibernate mode uses the hiberfil.sys file to store the the current state of the PC, and since it's managed by Windows, you can't delete the file. So if you never use it, and want to disable Hibernate mode, you'll need to open a command prompt by right-clicking on the Command Prompt in the Start menu, and then selecting 'Run as Administrator'. Now, type in the following command:
powercfg -h off
Once you exit the Command prompt, You'll notice that the Hibernate option is now gone from the Shut Down menu. You'll also notice that the Hiberfil.sys file is now gone from the Windows directory.