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I'm thinking of installing an SSD on my machine at home, and the easiest way to do this is basically to clone my current hard drive over to the new SSD. Trouble is, if I right click on my current hard drive and select properties, my used space is 230GB, thus requiring me to buy a monster SSD.

However, if I right click on each of the top level folders in my hard drive and select properties, the total space used by those folders is only 140GB. 100GB of that is music and movies, which I can easily clean out before the move to the SSD.

So here's the rub, where did the other 90GB go? For the life of me I can't figure it out. Shouldn't the sum of the used sizes of all the top level folders in your C: drive roughly equal the used size of the C: drive itself?

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This may not be a directly addressed to your question but in buying a SSD it may not be necessary to get one which has comparable storage capacity as your current HDD. If it's speed (of read and write) your after it might suffice to buy a SSD of less storage capacity, say 80 GB (they seem to be reasonably priced now), and on it your put the system files (the OS and the programs) aswell as the files your currently working on. Then you just store whatever other files your not currently working on, or don't need hasty read and write for (these could be media files), on your current HDD. – N.N. Jun 30 '11 at 13:16
Everything you've said is true. Unfortunately, I couldn't figure out a way to easily move Windows without formatting my current drive, and I can't find the DVDs for half the stuff I have installed. I know I know, that's my fault, but just doing the image will the whole process go so much smoother. – WindyCityEagle Jul 1 '11 at 2:43
Keep in mind that the size of each file is quite different than the space it takes on disk. Uncompressed files take more space on disk than they actually are in length, compressed files can take less. – Mooing Duck Apr 12 '13 at 0:43
up vote 10 down vote accepted

There are hidden files and directories which contain system files that are not included in the calculation. System volume information, for example, contains your system restore points and volume shadow copies among other things. It is not included in the calculation because by default the ACL does not allow your user account to view the folder or it's properties. You can gain access to it if you really want to, however.

On another note, the cleanmgr.exe utility (better known as Disk Cleanup) can help you reclaim most of your disk space. The More Options tab allows you to delete all but the most recent restore points and Volume Shadow Copies.

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Ahhh, More Options. That's what I was missing. I hadn't figured out the secret Windows 7 trick to make the more options tab appear. Turns out I had 90GB of System Restore data. – WindyCityEagle Jul 1 '11 at 2:41

Use WinDirStat to see where your files are taking up space:

It is free, lightweight, and there is no easier way to see your usage by directory.

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Thank you. This is a great utility app. I was using Folder Size which is good, but it skips some files. – Hong Jan 12 '15 at 15:50
This is exactly what I was looking for – Kerry Jones May 23 '15 at 11:38

I recently had the same question, but I stumbled upon the answer. Symantec Norton was scheduled to periodically backup files by storing them on my hard drive. I found the folder containing the backed up files and discovered that these backed up files added more than 100 GB to the quantity of data stored on my hard drive. Because I frequently back up my modified files and folders onto removable hard drives, flash drives, etc., I do not need the Norton backup utility. I simply deleted the files and canceled future Norton backups. The resulting increase in space on my hard drive was enormous.

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Hidden swap file/directory (recycling bin?) in the root directory?

Also does the windows explorer in win7 consider hidden files inside those directories when tallying it's total?

Just a couple guesses.

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In may case it was the page file dll that occupied around 6GB and the hibernet.dll file that occupied around 2GB.

If you enable "Show protected operating system files" then you can see those two files.

You cannot and should not directly delete the files. If you really need some space and want to remove the files please google for the proper procedure.

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Here's a comprehensive list of all the reasons I can think of why the used space in a hard drive may be greater than the sum of the file sizes. OP has already solved his/her problem, but the issue may remain for some lurkers.

  • A file takes up more space on the disk than merely its size. For example, a text file that contains the letters "hello" has a file size of 5 bytes, but it also takes up space in the filesystem's table to store its name and properties. Usually the difference is not greater than a few hundred bytes, but if you have many tiny files, that can add up to quite a bit. You can see the difference by comparing "Size" and "Size on disk" numbers after opening the properties dialog of a file in Windows' file explorer.
  • You may be forgetting to check hidden files: make sure you have "show hidden files, folders and drives" enabled in Windows' file explorer options.
  • You may be forgetting to check system files: make sure you have "hide protected operating system files" disabled.
  • You may be forgetting to count the recycle bin which is a special case of hidden and system files.
  • Contents indexing takes up space: if you open the properties dialog for a partition, you can see the option "Allow files on this drive to have contents indexed in addition to file properties". This takes up space, I'm not quite sure where on the file system.
  • Previous versions (or shadow copies or file history) take up space: NTFS has the feature of shadow copies of files, which takes up space not counted in the plain file size.
  • You may have enabled compression: this should theoretically cause the used disk space to be smaller than the sum of the file sizes, rather than bigger, but in any case, it's a spanner in the works. You can check by opening the properties dialog of a partition in Windows' file explorer.

Also, remember that you may have hidden partitions, or unallocated space on your hard disk where you could have a partition. Open "Disk Management" shipped with Windows to check this.

If anything is missing, go ahead and edit my answer to make this as comprehensive as possible. I'm happy to make this a community wiki post.

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