I have a standard personal computer, (450Gb hard-disk, 8 gb of RAM) with Windows 8.1.

I do not have loads of files on the hard drive (around 20 gb programs included) I was wondering how is it possible that the used disk space is around 120 gb? Furthermore every two weeks or so, Windows eats up another 5-6gb and fills it with who knows what. Is there a reason for this?

I regularly delete "shadow copies" and get back a few gb from time to time, use C-cleaner, do disk defragmentation and every suggested maintenance procedure, nevertheless the space used is still going up. Shadow copies and backups within the pc in my experience are pretty much useless since when it crashes it goes all the way down and the only thing you're left with are the file in the hard disk if you're lucky (external backups are usually the way to go IMHO).

What can I do to free disk space and, more importantly, stop Windows from eating it all up?

PS: I do not intend to pick on Windows, since I grew up with it and still use it heavily with some specialized programs and find it really good at performing most of what I need, however this thing really bugs me. How is it possible that a fifth of the hard disk is used by Windows only, when Linux (on another machine I installed Linux for me to try) on the other hand uses much less than 20 Gb???

  • 2
    A program like WinDirStat will help you identify where your space is disappearing to.
    – Burgi
    Nov 26, 2015 at 14:40
  • @Burgi thanks, I'll definitely try it, however this thing happened on Windows 7 too, and by talking with some colleagues, they experience similar things, so I would like to know if it is the OS that is doing something behind the curtains. I ask this because on Linux and Mac it does not happen at all. As far as I remember, it did not happen on Windows xp.
    – mickkk
    Nov 26, 2015 at 14:44

1 Answer 1


A quick Google returns a lot of complaints about Windows 8.1 using a lot of space.

According to Microsoft the standard installation requires 20GB. The standard install of Ubuntu is about 15GB, OSX appears to be roughly the same.

Most operating systems use the harddrive as additional system memory (virtual memory). This is called the swap or pagefile, in linux installations this is usually a dedicated partition called /swap. As this is a dedicated partition you rarely see it impacting upon your storage/operational partition.

Under Windows, virtual memory uses a file on the main partition called pagefile.sys. My system isn't doing any heavy lifting at the moment but software like PhotoShop or Visual Studio would massively increase the amount of virtual memory needed by the OS. In turn my disk usage would increase.

Screenshot of the pagefile in Windows 10

In your question you state you have shadow copy running. This would also gobble up disk space as the Shadow Copy service takes a snapshot of every changed file every few hours. Shadow Copy is turned on as default in Windows 8 as part of system restore. Turning this off will save a significant amount of space.

Tools like WinDirStat will help you pin down where your storage space is going.

  • I accepted your answer because I found it informative, thanks. After some research and disk cleaning and inspecting, I found out that apparently 70 Gb are "documents" (certainly not mine), if 20Gb is the operating system, then 50Gb is unknown (at least to me) stuff. I suspect some heavy programs such as Matlab and Autocad are hiding tons of files who knows where.. By using basic windows tools I was able to delete a lot of example videos/plugins/helpers and stuff I'll never be using.
    – mickkk
    Nov 27, 2015 at 16:48

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