Did the Windows 10 Fall Creators Update “Balloon” Your VM? Here’s How to Fix That!


Microsoft released the long-anticipated Window 10 Fall Creators Update on October 17. With new features like the People Bar (as well as Cortana and Edge improvements), many Windows 10 users were looking forward to this update and installed it right away. I was one of those who did so.

The features and stability improvements were great, but people also noticed that the update significantly increased the amount of space that Windows 10 occupied on their PC—or in the case of Parallels Desktop® for Mac, the size of the virtual machine on their Mac.

In my case, my Windows 10 VM ballooned from 16.37 GB to 37.51 GB because of the update. (See figure 1). I had expected it to enlarge, but not by 21 GB!

Figure 1_VM sizes before and after

After talking with others and doing a little research, I determined that the bulk of this 21 GB expansion comes from Windows 10 storing a copy of many files, in case the user wants to “undo” the update.

I don’t need this undo protection for two reasons:

  1. I already have the ultimate undo option available: I installed the Windows 10 Fall Creators Update on a copy of my main Windows 10 VM. I always do major updates or installations of alpha or beta applications on a copy of a VM. In case a problem develops, I can just throw away the copy. If no problems develop, I can throw away the original. This is one of the many ways that VMs provide you with options that a hardware PC cannot.
  2. In the past, I have set Windows “restore points” on a hardware PC before an update or other major action. But when I tried to do a system restore to such a point, I got the alert from Windows: “Sorry, Windows cannot restore that restore point.” So I have never trusted these to work. For me, an undo operation has to work 100% of the time, with no possibility of failure, or it is not a reliable undo.

Thus, this 21 GB was a waste to me.

It turns out that it is not difficult to recover this disk space. Just use the Disk Cleanup utility, and be sure to click on the “Clean up system files” button. For me, doing so increased the disk cleanup recovery from a paltry 73.2 MB to 27.2 GB! (See figure 2.)

Figure 2_Cleaning up the system files can make quite a difference

Windows very properly warns you that proceeding with this disk cleanup has consequences. (See figure 3.)

Figure 3_Windows warnings

I proceeded, and in the end my VM was 18.93 GB in size, so I recovered 18.53 GB space on my Mac. (See figure 4.)

Figure 4_Final result

While I am primarily concerned with space occupied by my Windows 10 VM, the same actions outlined here will also work for a Windows 10 hardware PC. Let your friends running hardware PCs know about this.

Tell us about your experiences installing the Windows 10 Fall Creators Update in the comments.

If you want to try Window 10 Fall Creators Update on a VM with Parallels Desktop 13, feel free to get started with our risk-free 14-day trial.

Kurt has been a Mac developer since before the Mac came out. Today he is the Senior Product Manager at Parallels where he works on both Parallels Desktop for Mac and Parallels Access. Prior to Parallels, he was the Senior Mac Evangelist in the Macintosh Business Unit (MacBU) at Microsoft Corp. Kurt is the author of three books and has lectured internationally on object-oriented programming, UI design, and virtualization. Kurt is also a Microsoft Office for Mac and iOS Accredited Support Professional for 2014 and 2015. Outside of work, Kurt has been a fencer for many years, has four times been a member of the US team at the world championships, and has also been the coach of the US team: http://www.naginata.org.

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