My Vista 64 installation has drive C, a 150 GB hard drive. I also has a 1.5 TB drive D. My C drive has 12.3 GB free. I don't know what's using up all the space. There's almost 83 GB unaccounted for!!!

As per this question and this question, I downloaded WinDirStat and SpaceMonger. WinDirStat, once I found the right options, tells me there's 82.9 GB of . SpaceMonger, which has a particularly nice display of the data, tells me there's 82.3 GB "Unscanned", with 2 unscannable folders.

Where do I turn now? Both tools roughly agree there's a large amount of data on my drive, but neither seem to be able to tell me what.

I've tried the standard approach; disk cleanup, remove hibernation file, set the virtual memory to the D drive instead of the C drive.

  • If you click on the . in WinDirStat and choose properties, what happens?
    – JP Alioto
    Aug 14, 2009 at 1:40
  • Can you post a screenshot from WinDirStat? Aug 14, 2009 at 1:42

6 Answers 6


It could be the System Restore service (and previous versions) eating that space up. Those are stored in the hidden \System Volume Information folder in the root of the drive. If you open an administrative command prompt window you can view the usage of System Restore/Previous versions by issuing and reading the following command

C:\Windows\System32> vssadmin list shadowstorage
(program output follows)
For Volume (C:)\\?\Volume{some-guid}
Used Shadow Copy Storage: 5.317 GB (3%)
Allocated Shadow Copy Storage space: 5.806 (3%)
Maximum Shadow Copy Storage space: 7.448 (5%)

If you find that they're using a large amount of storage you can issue the command vssadmin Delete Shadows /For=C: /Oldest to delete the oldest shadow copy.

You can set the Maximum Shadow Copy Storage space to 12GB with the following command:

vssadmin resize shadowstorage /on=C: /for=C: /maxsize=12GB

  • You hit the answer right on the nose! Presumably this is caused by my use of the excellent Rebit backup software, though this is a very nasty side-effect. Thank you. Aug 14, 2009 at 2:29
  • Joshua's answer solved my very similar problem, and I haven't used Rebit. Aug 19, 2009 at 20:06
  • 1
    several years later and with Windows 10 this is still a problem but fortunately the answer is still valid ;-)
    – t3chb0t
    Mar 25, 2017 at 19:04

Joshua's answer is probably the most likely, but have you ever used Offline Files on this computer?

The client side cache (CSC) may not properly empty, even if offline files is disabled.

You'll want to delete the contents of %systemroot%\csc to clear it up (or at the very least, verify that this is the information that is taking up the space.

MS KB article on the CSC.

  • I haven't, but thank you for bringing it up in case anyone else runs into the problem. Aug 14, 2009 at 2:29

You could alternatively try JDiskReport to analyse your disk.

  • Thanks, for some reason, even when I checked the users folder, it didn't count Google Drive. Jun 16, 2019 at 16:49

I like SequoiaView. It lets you drill down into directory structures to see what's using the disk space.


You should also check the C:\ drive for a file called "hiberfil.sys". I had one that was wasting 7GB of disk space. (It's size is based on the RAM in your machine).

This file is used for Windows hibernation, but if you don't need to hibernate your PC, you can disable hibernation to get rid of the file.

To disable hibernation and remove hiberfil.sys, check out the instructions for your version of windows here: http://www.howtogeek.com/howto/15140/what-is-hiberfil.sys-and-how-do-i-delete-it/


There are all sort of reasons why disk space can be overused, and this is a job that System Admin people have to deal with all of the time. One common reason is the Virtual Memory page file, which is related to how much RAM you have. In the end, it might be a bunch of log files buried deep somewhere in folders, or a hidden "media" stash, or whatever, so a tool to visualize the whole drive is very useful. My tool of choice in this regard is spacemonger, but there are others.

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