Why did 30 GB of space disappear from C drive in less than one week?
Question by Nancy Cummings /

I have difficulty opening MS Word, Excel, etc. I noticed that 30 GB of memory was missing since last week. I ran Malwarebytes, found nothing, Kaspersky deep scan, found nothing. I downloaded nothing. But, last week, I compressed some documents. I thought this would make more space. Operating any program is time consuming. How do I find out what happened?

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Answers (29)
  • Matthew McNamara

    So this is a bit out there in terms of the realm of possibilities, but the same thing happened to me last week. I used WinDirStat (http://windirstat.info/) to visually show me the largest files and it turned out there was one 20+GB file that had eaten up my SSD space.

    Turns out it was a log file. When I googled the file name it was an arduino log file that grows huge if you disconnect the usb from the board (generating a serial error) and keeps growing until you close and open the ide again. If by any chance you are playing with an arduino, it may be worth looking into.

  • Gaurav

    This can happen, if crash files and dump files are created by windows. Also at some point windows also keep shadow files which are used as a restore points. These also gets accounted towards 30GB or more sometimes. it depends on what system you have (OS) and how it was functioning till the time you recognised this issue.

  • Sohel Zaman

    Trying using TREESIZE free/pro. You can see all the details of every file which occupies how much space in that particular drive. That way, you may be able to find out the missing 30GB.

  • Ben

    Try using the Disk Cleanup tool, just to rule out clutter from unnecessary files

    • Nancy


      Still same. I ran WinDirStat. Found over 40GB of Kaspersky log files.

  • Oron

    I’d suggest using Space Sniffer, which I prefer to WinDirStat (but both are pretty similar, to be honest). These will show you which folders & files are taking up the most space.

  • illegal3alien

    My favorite is WinDirStat. Like other programs, you run it and it will report what files are taking up the most space. After it finishes, but click the largest boxes at the bottom and it will tell you what the file is. If you’re not sure, report back with information on the file name and location and someone should be able to tell you what it is and how it got there.

    • Nancy

      I downloaded WinDirStat as you recommended. It seems that most of the new files are related to Kaspersky. There is something very strange. There is a “Change” dated 7/24/2012. However, most of this is Kaspersky. I cannot understand how or why this would happen. I will contact them. There are other video files from years ago that are taking up lots of space, but they have been there for years. This is all since July 4. The largest Kasperky file is 17.0 GB dated 7/10/12:
      C:\Documents and Settings\All Users\Application Kaspersky Lab\KAV.
      another is 5.0 GB dated 7/13:
      C:\Documents and Settings\All Users\Application Data\Kaspersky Lab\KAV.

      What next?

      BTW, Thanks for recommending WinDirStat. I think it is great! I found some old files and plenty of duplicate files as well. Is there anything that will remove duplicate files found in different places?

      I see strange times changes took place as well such as today at 11:42:30 PM when at this moment in time the date is correct the time is 8:53 PM.

    • Arrow Quiver

      Since these are just log files (not quarantined apps/files or anything), then I would probably say it’s safe to remove.

      Or maybe all of the other .LOG files under this folder:

      C:\Documents and Settings\All Users\Application Data\Kaspersky Lab\

    • illegal3alien

      I would be careful deleting both of them. Logs that big indicate either Kaspersky is malfunctioning, or having some sort of problem. I would download http://download.cnet.com/Large-Text-File-Viewer/3000-2379_4-90541.html to open up the logs and save a big chunk of the bottom. The resulting file should be around 10MB. Once you save the last chunk of each file, Kaspersky will probably want this to help determine why the program is logging so much information. If it says the file is open in another program, try temporarily disabling Kaspersky. You may also need to go into services.msc (Start > Run) and look for any Kaspersky services and temporary Stop them (by right clicking). After you get the files removed, restart the computer to be sure Kaspersky gets restarted and running again.

  • Mihovil Pletikos

    when you said missing is that it is gone from the disk space of just used up?
    if it is gone from the disk space maybe you have some errors on the drive. if not install ccleaner and just run it to find if something can be recovered

    • Nancy

      I should have clearified better. I had about 95-100GB free space (total 293) now about 64-70GB. I am not using that computer right now so I do not have exact numbers. Total space remained the same.

    • Nancy

      I started noticing early last week. Cleaned everything and recovered 3 GB by compressing my documents, deleting cookies, temp files and old stuff.

      Then I had more trouble booting and once last week, I checked space and saw nearly 35GB was used up somehow. I was totally stumped. I did not download anything but I did leave the computer running a couple of nights while I scanned for viruses and malware. All this occurred since last weekend, July 6 or 7.

      The drive space was used not missing. I should have made it clear in my original inquiry.


    • ed little

      Could you be supplying your extra space to the “cloud” for use as storage space by other people?

      Where is the “cloud” anyway?

    • Nancy


      Thanks for your inquiry. I found that my new Kaspersky subscription offered an option to participate in Kaspersky’s Security Network. The storage space was used by Kaspersky’s log files. Nearly everything my computer did was logged. I have since then removed my option to participate and communicated with them regarding the space used.

      After installing and running WinDirStat, I was clearly able to see the largest files that changed overnight were Kaspersky’s log files.

      I have had many hours of successful operating since I removed my participation with Kaspersky’s Security Network.

      Things are now working fine. My computer is getting pretty old and I have no intention in replacing it.

      As far as the “cloud.” I have no idea where it is, only that there is lots of space in the cloud. FOrtunate none of is supplied from my hard drive.


  • Rob Douglas

    I’d try having a look at the results of WinDirStat – http://windirstat.info/. It’ll show you exactly where the space is being consumed

  • ha14

    download Treesize free version and do scan, see where are the big files and check if they match 30GB

  • Alan Wade

    How many hard drives do you have? If space is a problem on the system drive usually C then look at moving the page file will free up many gigabytes of space.
    This can also be your problem if you have been using specialised cleaners which would delete the pagefile then recreate it. Of course if the pagefile gets corrupted then that can give you a sudden loss of space.

    To move it assuming you have either a partitioned drive or an extra hard drive is very easy and you will see the difference directly and you should see a difference in overall performance.

    To move it click on Start, right click on Computer and select properties.
    In the left hand pane select Advanced System Properties.
    Click the Advanced tab then in the ‘Performance’ section select Settings.
    Now click the Advanced tab and in the Virtual Memory section select Change.
    Uncheck Automatically Manage Paging File Size for All Drives
    Choose the drive/partition where you want your pagefile to be stored and select System Managed Size from the list of options then press Set.
    Select your system drive (usually C) click on Custom Size and make the Min and Max 1000 MB.
    OK your way out and reboot.
    Your pagefile will now be rebuilt which will temporarily slow down down your computer for a little while. So its best to do this just before you are going out etc.

    Of course as I said there was a couple of assumptions there with drives and partitions but that will free up space on your C drive and give you a little performance kick.

    • Nancy

      C and D I will do as you say and see what will happen.
      Thank you.

    • Bruce Epper

      Just a few comments about playing the the pagefile:

      1. Reducing the size of the pagefile may have a NEGATIVE impact on system performance based on the amount of RAM in the system and how the system is used during normal operation.
      2. You will get better performance if the size of the pagefile is a power of 2, so instead of making it 1000MB, make it 1024MB.
      3. Many systems have a single hard drive partitioned into 2 parts and thus having 2 drive letters. Moving a pagefile from one to the other will have no impact on overall performance since it is still residing on the same physical device.
      4. Those systems that have a single drive with two partitions generally have the second partition configured with the image that is used for the manufacturer’s system restore operation (not to be confused with the Windows System Restore). It should be set up as a read-only partition, so you may not be able to put anything there anyway, but if it isn’t you run the risk of damaging that restore image so do this with extreme caution.

      If you do not hibernate the computer, you can always turn that off and reclaim the space used by hiberfil.sys on your system drive. To do this, open an elevated command prompt (Start -> type ‘cmd’ (no quotes), right-click cmd.exe and select ‘Run as administrator’. Type ‘powercfg -h off’ and press Enter. Close the command prompt by typing ‘exit’ and pressing Enter.

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