System Files Take up 85GB

If you don't use Hibernation, you can disable it from Powershell, and that will remove the hibernation file.

If you are quite sure that you won't want to restore any of your backups, you can remove those, but the proper way to remove them is with the backup program that originally created them. Simply deleting them may leave behind configuration files and registry entries.

The other folders should not be touched. In particular, if you remove the hidden C:\Windows\Installer folder, you will likely find it difficult or impossible to repair, update or uninstall your currently installed applications.

Let's do some math: If there are no files that are greater than 1 GB ("there is no huge or gigantic file in my PC") and only a few files between 128 MB and 1 GB, and yet you have 78 GB of system files, then you must have thousands upon thousands of small files less than 128 MB each. Can you identify them?

(Did you include hidden and protected system files in your searches?)

By now, you are becoming aware of the way I work: I go by the book, and I'm thorough. Were I in your situation, I wouldn't delete anything without a good understanding what it is, and then I would make sure to remove it in the way it was designed to be removed. This approach, more than anything else, has allowed me to have trouble-free, stress-free computing for a long time.

But it's a big world out there, with many different approaches. You may find another approach that you prefer, which is alright with me. After all, it's your computer and you need to do what you think is best for you.

Were I in your situation, one of my considerations would be the possibility that my computer was hacked. More specifically, I would suspect that my computer may be part of a botnet that is doing work for someone else.  This is distressingly common on the internet, and your anti-virus software won't pick up on it because the attacker's work that your computer is generously doing is not intrinsically malicious. Unless you've installed very many huge programs, or you have seriously interfered with your copy of Windows, there's just no way that a Windows computer has 78 GB of system files under normal circumstances.

Do you know how to setup File Explorer to display files from largest to smallest in size? Or how to display only 'Gigantic' (> 4 GB) or 'Huge' (1 - 4 GB) files? If not, no problem, we'll show you how.

What are the biggest files?

Thank you for replying Sumit. 

Yes, of course there is an update pending, because there isn't enough space for the update. For it to be done, I have to take out something first. That's how I realize the system file is ridiculously large, and I am not going to put up with it anymore.

Thank you for replying.No, I don't know how to use the file explorer for this, but as you can see in this screenshot with the files shown,

the largest single files are pagefile.sys and hiberfil.sys in the root directory. The others are all within 1 GB I think. Probably I want to ignore the pagefile, while I wonder if I can do something with hiberfil.sys because I won't need hibernation and that 2.9GB of space is much needed.

Hi Shira,

I am Sumit, an Independent Advisor and a 2-Year Windows Insider MVP here to help.

The biggest problem I could interpret in the screenshot was the huge SoftwareDistribution folder. Is there an update pending?