Where has all my disk space gone?

25% of the disk gone!  The game’s afoot!

50 GB of disk space missing doesn’t sound like much, but when it’s on your 220 GB SSD it’s a fair old chunk of change.  I had my suspicions that the space of all the folders and files didn’t add up to the usage figures on the disk and after a few Powershell shenanigans I was proved right.

Enter WinDirStat.  A lovely free tool that gives you a breakdown on your disk usage.  Unfortunately, there was still a chunk of missing disk.  I fiddled with the options and it listed the 50GB of space as ‘Unknown’;  it was listing the disparity between the free space on the disk and the total size of all the files and folders.

WinDirStat In Action
WinDirStat In Action

So far, so joyless.  But one of the reasons WinDirStat (or me) might not be able to see some stuff is due to permissions.  Re-logged in as Administrator and there you go;  50 GB in the Recycle bin!  Hooray!  Emptied and loads of lovely space back.

A few days later,  40GB was missing again 😦  And it wasn’t the same cause.  Ran WinDirStat again as admin and it couldn’t see where the space went.  Admin couldn’t see it, so it couldn’t be a permissions issue again.

OR SO I THOUGHT.

There’s plenty of folders and files that are restricted to Local System; the true ‘God’ account on your local Windows box.  You can see these hidden folders as admin but you can’t enumerate them (as you don’t have permissions).  The problem is you can’t log in as System very easily;  Microsoft stop you doing it for all sorts of reasons (you can break everything;  it’d be a security hole;  people would be sad).  But there is a way.Well, several ways but the I used was as follows;

  • Use psexec.exe from SysInternals.
  • Run  psexec -i -s cmd.exe as an admin.
  • Use the system account cmd prompt to run WinDirStat.

And all was revealed!  In this case it was an orphaned CSC system folder.  But it could have been a few things lurking around; offline files, system recovery data, roaming profiles (with restrictive permissions) etc.

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