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I have a drive partitioned so it is seen by Windows as 2 drives: C:\ and D:\

Windows 7 shows D:\ as full up in the graphical summary in 'My Computer' summary of all the drives, e.g. the bar graph indicates full and nearly all of the drive's capacity, 108Gb, is full.

So I go into the D:\ drive to look at the files, I see several folders. I select them all and the right-click menu Properties to count their size, expecting the value to be about the same as what Windows reports in the summary, i.e. nearly 108Gb. But the properties window shows the files are very small, Kbs and Mbs, nowhere near 108Gbs.

One of the folders is a backup, but its size is very small.

I've checked the folder options to show all system files and hidden files too - and counted these in the properties.

Something invisible is holding the space.

What is happening here?

I'm afraid to delete anything if it removes valuable backups.

Have I got huge backups here? Why can't I see them? How do I see them?

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Thanks folks very very much for all your useful suggestions. I've credited many of them with votes and I will accept an answer this week. Sorry for the delay. I'll chat to my friend and see how the suggestions work out. Thanks again. –  therobyouknow Apr 5 '10 at 11:02

8 Answers 8

Good you ruled out the possibility of hidden or system files not being calculated in the file size sum. Some other things to check:

  • Disk corruption: run a chkdsk -f on the disk. Maybe there is a corruption of the filesystem and the FAT (or the MFT, the NTFS equivalent) thinks disk space is allocated while it isn't.

  • Invalid free space reporting: NTFS stores the free space in its metadata. It's possible it's invalid. A chkdsk -f should fix it too.

  • Insufficient permissions: is your user allowed to see and access all files on the disk?

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Thanks +1 - this is the best answer so far... I will suggest to my friend to try these or I will when I next see them. It's their machine BTW. –  therobyouknow Mar 30 '10 at 12:44
    
Does chkdsk -f incorporate checking for "ADS" as mentioned by Synetech inc. below? –  therobyouknow Apr 8 '10 at 8:28
    
yes, as it's part of the metadata. AFAIK ADS is mainly used for setting a flag on files downloaded from the Net, so you're asked for extra check when you run them. Now if a program would store massive data in the ADS in the correct way, chkdsk would not fix anything. –  Snark Apr 8 '10 at 8:46

Maybe WinDirStat could help identify a file you missed as well.

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+1 Thanks for what looks like a useful tool. –  therobyouknow Mar 30 '10 at 12:46

I answered a similar question for Windows Vista. Chances are it is volume shadow copy that is taking up the space, which will not show up when you select all files and folders and look at their properties.

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Is D:\ an NTFS drive? If so, then one or more files could have an Alternate Data Stream which is a way of attaching metadata to a file. They are normally invisible to the filesystem, so you need a tool like an ADS viewer. Usually the metadata is small, but there is nothing stopping a file from having a massive file attached to its ADS. (Malware also likes to hide in the stream.)

Sysinternals offers the (free) utility Streams to can view/delete ADS. Open a command prompt and run streams -s d:\*. It should show you all of the alternate data streams of all of the files on the drive. Then you can use the -d switch to delete any large, unwanted ADS.

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Thanks +1. Would chkdsk -f be another way of revealing the ADS? As suggested by @snark above? –  therobyouknow Apr 8 '10 at 8:25
    
CHKDSK does not display ADS as far as I can tell. The /f switch just tells it to fix errors, so that does not help either. The /v switch tells it to show what it is checking, but that only seems to work on FAT32 drives, not NTFS (and so it does not show ADS). You’ll need a tool that is specifically meant to show the streams. –  Synetech Apr 8 '10 at 12:40

You can use the good old DOS prompt (Command prompt) to find out information about all of the files in your directory, navigate to the directory that you are interested in using Windows Explorer and click the Right Mouse Button and the Right Shift key at the same time.

A context menu will pop up giving the option of "open command window here".

You will now have a DOS prompt in the directory you are interested in, use the following command to list all of the files in the directory and their sizes:

dir /a
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You will also want to add the /s switch to recurse into all subdirectories. –  Synetech Mar 30 '10 at 13:30
    
+1 for this command +1 to Synetech inc. –  therobyouknow Apr 5 '10 at 11:00

I would have an answer, if this problem would occur on a Unix system ;-)

On Windows, I suspect, it's related to "File Streams": a single file might have a number of associated streams, which each have their own allocation size and data size; depending on which stream you're opening, you will see different sizes for the same file.

Once again: I'm a Unix guy with only limited Windows knowledge; nevertheless, I hope this helps.

Enjoy!

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" a single file might have a number of associated streams, which each have their own allocation size and data size; depending on which stream you're opening, you will see different sizes for the same file" thanks - and how do you find this out? –  therobyouknow Mar 30 '10 at 12:47

If there are a lot of individual files, then it could be "slack space" as a result of how storage is allocated. When you look at the properties, do you see two sizes indicated? (On XP, they are "Size" and "Size on disk", not sure about on 7).

Another possibility is the "System Volume Information" folder. DON'T FIDDLE WITH IT. It can sometimes get quite large, but finding out is difficult as you can't normally access it. It's used for the system restore functionality.

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I don't think there are many files, only like 10 or so - thx for suggestion anyway. System Volume Information" folder - when I last looked (this is a friend's machine) - this was small. But what is it? What tools could be used to look inside. –  therobyouknow Mar 30 '10 at 12:43
up vote 0 down vote accepted

The answer is a composite than comes from several people - thank you to those - credited usable answers with +1 point. I don't think it is fair or accurate to award the answer to just one of you. Unfortunately superuser doesn't allow accepting multiple answers. I deliberated over it but thought self-answering but crediting you all with mention and rep points would be the best option. So for the following users I will try your answers in that order:

Joshua, Richard, snark, Adam Driscoll, Synetech inc.

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