Windows Updates – CAB Files Filling Up Hard Drive


It was a dark and stormy night and all was well in my little world of Windows until …

I noticed that the system performance of a particular Windows 7 workstation was horrible!  Moreover, I was unable to install a plethora of critical Windows updates.  As you might know, the “Admin 101 Play Book” states, “In the event of poor system performance, first check the available system resources,” so I quickly looked at the system hard drive free space of this sluggish workstation.  Great Scott!  As I suspected, the system hard drive was near full capacity!  After further investigation, I was able to isolate the problem to the following folder:  C:\Windows\Temp.  No worries, this should be an easy fix, right?  I clicked inside the “C:\Windows\Temp” folder, pressed Ctrl+A on the old trusty keyboard which selected all the files, pressed the delete button, and emptied the Recycle Bin.  Boom!  That just happened!  Easy peasy lemon squeezy!  Unfortunately, it wasn’t long before the dreaded cabinet files (i.e., .cab files), began to download into the “c:\windows\temp” folder again.  NOW WHAT?!

I knew that Windows Update was automatically configured on the client to download updates from our internal Windows Server Update Services (WSUS) server and something was running amuck!


  1. Open Services – Click on the Windows Start button and type the following into the “Search programs and files” box:  services
    Click on “Services” when you see it appear at the top of the search list.  Keep Services open until all the steps have been completed.  Launch_Services
  2. In Services, right-click the “Windows Update” service and select “Stop” to stop the service.  Services_mmcWinUpStopped
  3. Open Windows Explorer – Right-click on the Windows Start button and select “Open Windows Explorer” from the contextual menu.  WinExplorerLaunch
  4. In Windows Explorer, delete all the files in the C:\Windows\Temp folder.  Keep Windows Explorer open until all the steps have been completed.
  5. In Windows Explorer, rename the “SoftwareDistribution” folder to “SoftwareDistribution.old”
    • C:\Windows\SoftwareDistribution => rename to => C:\Windows\SoftwareDistribution.old
  6. In Services, start the “Windows Update” service.  A new “SoftwareDistribution” folder is created.  Services_mmc_WinUpStarted
  7. In Windows Explorer, delete the “SoftwareDistribution.old” folder.  This will remove all the previously downloaded Windows updates.
  8. In Services, right-click the “Windows Modules Installer” service and select “Stop” to stop the service.Services_mmc_WinModInstStopped
  9. In Windows Explorer, delete all the files in the C:\Windows\Logs\CBS folder.  If you are unable to delete the “CBS.log” file, switch over to the “Services.mmc” and refresh the window to update status of the “Windows Module Installer” service, stop the service, and switch back to Windows Explorer to delete the “CBS.log” file.
  10. In Services, right-click the “Windows Modules Installer” service and select “Start” to start the service.Services_mmc_WinModInst_Started
  11. At a command prompt, type the following:  wuauclt.exe /detectnow cmd_wuauclt
    • This will force the Windows Update service on the workstation to query the WSUS server for its needed patches.
  12. The end.

Author's Tidbit:  WSUS uses a cookie on client computers to store various types of information, including computer group membership when client-side targeting is used. By default this cookie expires an hour after WSUS creates it. If you are using client-side targeting and change group membership, use the /resetauthorization option in combination with the /detectnow option to expire the cookie, initiate detection, and have WSUS update computer group membership.

Note that when combining parameters, you can use them only in the order specified as follows:

wuauclt.exe /resetauthorization /detectnow
What are Windows Cabinet Files?

A cabinet is a single file, usually with a .cab extension, that stores compressed files in a file library. The cabinet format is an efficient way to package multiple files because compression is performed across file boundaries, which significantly improves the compression ratio.

Large files can be split between two or more cabinet files. There can be no more than 15 files in any one cabinet file that spans to the next cabinet file. For example, if you have three cabinet files the first cabinet can have 15 files that span to the second cabinet file and the second cabinet file can have 15 files that span to the third cabinet file.

The installer extracts files from a cabinet as they are needed by the installation and installs them in the same order as they are stored in the cabinet file. The space requirements for installing a file stored in a cabinet are no different than for installing an uncompressed file.

A cabinet file can be located inside or outside of the .msi file. Beginning with Windows Installer 5.0 running on Windows 7 or Windows Server 2008 R2 the installer saves any cabinets that are embedded in the .msi file before caching the installation package.

Windows Installer 4.5 or earlier:  To conserve disk space, the installer always removes any cabinets that are embedded in the .msi file before caching the installation package on the user's computer.

Author’s Note:  For comprehensive troubleshooting information on both the WSUS server and client computers, see “Microsoft Windows Server Update Services Operations Guide.”

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