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  1.    09 May 2017 #1
    Join Date : Jun 2016
    Posts : 43
    Windows 10 Pro x 64

    Large discrepancy in C drive used disk space


    Could someone help explain why there is an over 5G difference in the used disk space on my "C" partition? The windows properties tab shows 33.3GB used, but I can't find where it's all being used. If I add up the space used for each folder, it only adds up to 28GB. This is also shown using WinDirStat:

      My ComputerSystem Spec
  2.    09 May 2017 #2
    Join Date : Feb 2017
    Home
    Posts : 479
    Windows 10 Home x64, V1709 (16299.64)

    Maybe Restore files?
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  3.    09 May 2017 #3
    Join Date : Aug 2016
    S/E England
    Posts : 4,490
    10 Home x64 (1709) (10 Pro on 2nd pc)

    Quote Originally Posted by CWGilley View Post
    Maybe Restore files?
    Quite likely. Restore points are held in the hidden 'System Volume Information' folder. You (and WinDirStat) don't have access to this so can't see what's in it.

    See Control Panel > System > Advanced system settings. On the System Protection tab, click Configure... to see how much is used by restore points.
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  4.    09 May 2017 #4
    Join Date : Apr 2017
    Posts : 6
    Windows 10 Pro 64bit

    I would guess any folder where the user does not have any access at all but system does, will make for that difference.
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  5.    09 May 2017 #5
    Join Date : Oct 2014
    Posts : 758
    Windows 7

    Quote Originally Posted by ChuckHL View Post
    I would guess any folder where the user does not have any access at all but system does, will make for that difference.
    Yes

    The value shown for total disk space used in the disk properties is maintained by the file system and is completely accurate.

    But for a variety of reasons, some quite complex, the file system does not keep track of the disk space used by individual folders. To show this in the folder properties requires a complex and potentially lengthy process. It requires examining the contents of each subfolder and each one it contains to check the file sizes. This could easily mean examining several hundred thousand file entries. There are all kinds of complications in doing this and the result is at best only an approximation.

    One big problem is with folders like "System Volume Information" which contains the restore points. Typical space consumed would be at least several GB. By default even an elevated administrator account (or even the built in Administrator account) has no access to it. The fact that Windows Explorer is a part of Windows doesn't give it any special privileges. If your account has no access, it won't either. This is necessary to maintain security. That means the attempt to examine it's contents stops right at the beginning and the size of the folder is seen as zero, and reported as such.

    WinDirStat has the same limitations as Windows Explorer.
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  6.    09 May 2017 #6
    Join Date : Jun 2016
    Los Angeles
    Posts : 1,031
    Windows 10 Pro

    Space Sniffer will tell you what is taking up the space. Most likely System Volume Information. As reported, you can limit the amount of space used for System Restore.
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  7.    13 May 2017 #7
    Join Date : Apr 2017
    Posts : 6
    Windows 10 Pro 64bit

    I would even dare to add (correct me if I am wrong) that if the computer has other users (C:\Users) any folder where the current account has not claimed access to, will show as size of 0 when its not empty.
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  8.    13 May 2017 #8
    Join Date : Oct 2013
    Posts : 25,194
    64-bit Windows 10 Pro build 17040

    Hello @sleepless,

    If you like, you can use the options in the tutorial below to help determine what is using up the drive space, and possibly free up some space.

    Free Up Drive Space in Windows 10 Windows 10 Performance Maintenance Tutorials
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  9.    13 May 2017 #9
    Join Date : Oct 2014
    Posts : 758
    Windows 7

    Quote Originally Posted by ChuckHL View Post
    I would even dare to add (correct me if I am wrong) that if the computer has other users (C:\Users) any folder where the current account has not claimed access to, will show as size of 0 when its not empty.
    Yes.

    If you are using a non elevated account (the default condition) it will not have access to the profiles of other user accounts and Windows Explorer will be unable to account for these files. In some systems this will account for a great deal of disk space. You really need to use an elevated account to get meaningful disk usage numbers for other than your own folders.

    There are utilities (such as Space Sniffer mentioned above) that use special techniques to enable access to folders like "System Volume Information". But do not expect exact results. Modern file systems are far too complex for that to be possible. And Space Sniffer needs to be used with an elevated account to obtain reliable results.
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  10.    13 May 2017 #10
    Join Date : Dec 2013
    Portsmouth Hampshire
    Posts : 1,829
    Windows 10 x86 14383 Insider Pro and Core 10240

    DISM ++ has a neat feature among many in its Toolkit - a File Explorer window that can open folders that normally are denied, even to administrators, without UAC etc. On the left, a normal File explorer window attempting to open C:\System Volume Information - with the usual "Access denied" dialog. On the right DISM++ File Explorer opens immediately the folder C:\System Volume Information - without any fuss or wait:

    Click image for larger version. 

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    DISM++ is a Chinese program, with much of its documentation in Chinese. It does not use Microsoft Windows DISM itself, but uses the CBS (Component Based Servicing) Reference API to reproduce the features of DISM in a graphical environment, making it a rather powerful set of tools.

    I'd put in a disclaimer - don't use it if you are not sure what you might be doing.
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