It’s a popular article because I think it’s a popular problem. I think anyone buying a new win 7 computer within the last couple years might encounter the CBS and CAB file problem if they need to do a bunch of updates to get their computer up to date. It’s a problem MS and most computer manufacturers are aware of but refuse to do anything about.

I bought a new Win 7 laptop from Dell in April 2016. The computer was made in September 2015 and so I had to install a bunch of updates/patches to get it up to date. When you do that, CBS persist files get generated that are bigger than 2 GB and can’t be compressed (zipped) by the algorithm Win 7 uses to compress. A bunch of fairly large CAB files are also generated. So these files keep getting generated and before you know it your hard drive is full. You can google this issue and get more details.

Here’s what I did when I discovered my hard drive was rapidly filling. I found the oldest CBS persist file that was over 2GB and dragged it to the recycle bin. Just doing that seemed to keep my hard drive from filling up (apparently the zip/compression algorithm works after the 2GB file gets removed – don’t know why) , and I haven’t had any problems with that since. The CBS persist files are found at Windows —> Logs —> CBS. Click on the CBS folder and you’ll see the files.

If you go to Windows —> Temp and open the Temp file you’ll see the cab files. On my computer there were literally a few thousand of them. They seem to come in sets of five, with one of them in a set being about 140 MB and the other 4 0 (zero) MB. I dragged a set of 5 at random to the recycle bin to see what happened, and I can not detect any effects on my computer function. I’m guessing you can get rid of them without any harm.

The CBS and Cab files are generated when updates/patches are installed on your computer, so there is a connection between them and Windows Update. Perhaps if some of them get deleted Windows Update won’t work properly. It does seem to work for me, but I have it set for “check for updates but let me choose whether to download and install them”. I end up doing almost all actual update installs manually, so even if WU isn’t working, I’d just disable it – as many folks here would recommend anyway.

Hope this helps I’m a self taught nontechie group B guy so you might well find better help from other forum members, but maybe the above will be of some use.

Still happening on my Win 7 Pro 64-bit machine.  Thanks for the reminder – was useful.  Please remind us every year.

I saw my c drive space disappearing, too.  However, when I followed the steps, my Windows Modules Installer service was already stopped.  I also did not have endless log files, nor endless cab files. So have to hunt for something else eating up disk space.

EDIT html to text

Hi everyone,

I deleted my post from late last night since, after further looking into this issue, I realized that my conclusions were not quite correct. None of my Win7 computers are compressing my CBS or CBSPersist logs. This perhaps is because I set Disk Space Usage under the Configure menu for System Protection to 40%, and perhaps because I periodically delete much older Restore Points after having made “known good” backups of the OS partitions. Note that the Disk Space Usage setting for System Protection is merely a “target” setting for how much disk space would be allowed to be consumed by Restore Points.

I have a suggestion for those who are experiencing this topic’s issue:

1. Set the Disk Space Usage under the Configure menu for System Protection to 40%. Remember, this merely is a target or maximum for how much disk space System Restore points would be allowed to consume. If this setting is set to a really low value, I have confirmed that, no matter how much free space you have on your OS partition, Windows will compress all CBS and CBSPersist log files into CAB files. I am not sure what % setting triggers the automatic log file compression into CAB files, regardless of how much free space you have on your OS partition.

2. Optionally, you might want to free up space on your OS partition if there is not much available free space on your OS partition. You could either move some data to another hard drive partition, or use a utility such as the free version of CCleaner to manually delete much older Restore Points that you no longer need. Those older Restore Points can consume quite a bit of space on your OS partition. When I say “that you no longer need”, I mean to say that you have a “known good” backup of your OS partition which was created on a later date than the older Restore Points which you want to delete. This feature to delete older Restore Points is under the Tools menu in CCleaner. You must manually select the older Restore Points which you want to delete. Note that you will want to configure the free version of CCleaner to NOT automatically start when Windows starts, and turn off the System Monitoring and Enable System Monitoring features under CCleaner’s Monitoring menu. I never let any cleaner utility automatically run. Instead, I always run them manually when I need to use them, and only after Windows has been running for at least 10 minutes. Why? Because some cleaner utilities overlap in what they can clean, leading to conflicts, and because Windows isn’t stable until it has been running for at least 10 minutes. Various delayed startup tasks run during those first 10 minutes after Windows started. If you are not familiar with using CCleaner, be careful about what optional settings you enable. For example, you could easily and accidentally delete all of your web browser passwords, or other important stuff.

3. Then follow the steps in Woody’s article for deleting all of the CBS and CBSPersist logs and compressed CAB files. New log files will be created after you reboot your computer in the following step.

4. Reboot after you have performed the above steps.

Now, and hopefully, Windows will not automatically compress all newly created CBS and CBSPersist logs. If you see that these newly created logs become quite large and rather quickly, perhaps within hours or after a day or so, then this most likely is due to issues which were created after partially installing updates and then hitting Cancel to stop the update installation(s). Fixing this issue is a separate topic.

Best regards,

–GTP

anonymous wrote:

I saw my c drive space disappearing, too. However, when I followed the steps, my Windows Modules Installer service was already stopped. I also did not have endless log files, nor endless cab files. So have to hunt for something else eating up disk space. EDIT html to text

Most likely, a ton of much older System Restore points. See my post about how to remove the much older ones which you no longer need.

Personally I solved the space “vanishing” issue with a different approach to use system tools… aka the Disk Cleanup feature ( and the further Administrator option offered after the Disk Cleanup popup finishes opening/loading ).

Since as Admin various system things, including old patches and logs, can be removed… it takes time, a lot of it, but I assume it’s the cleanest option too.