Today at work I was doing moving some files around when I realized that my C: drive, which has Windows XP on it, was running seriously low on disk space. A quick perusal of the drive uncovered a 1.5 gigabyte file called hiberfil.sys. Given that I never use the hibernation system in Windows I figured this was a prime target for purging, but the system wouldn't let me delete the file as it was locked by the system that controls hibernation. So, off a googling I went and found my answer on the very first result. Read on for a quick explanation.