I noticed that my hard disk was down to less than 1GB free this evening, so I decided to do a clear out. I am running a rather crusty old Windows XP Pro installation. On my usual rounds, I noticed a large file that I hadn’t noticed before, called “hiberfil.sys“. It was sitting in the root of the C drive, taking up around 1.5GB.
I’ve learned from experience (the hard way) not to go about randomly deleting files. This is especially important when Windows displays them with a slightly faded-out icon, indicating they are supposed to be hidden/system files. Thankfully, a quick web-search revealed what I needed to know.
Apparently, it’s related to Windows’ hibernation mode. That’s the kind of half shutdown mode which lets you resume exactly where you left off when you power-up again. The file stores all the stuff in your computer’s active memory, ready to be restored. The more RAM you have, the bigger that file will get. The way to prevent this space being taken up is to disable hibernation mode.
You can get more information about hiberfil.sys at SoftwarePatch.