Previous Windows installation files are files created while upgrading your Windows 10 installation to the latest build.
While upgrading Windows 10 install to the latest one or while upgrading from a previous version of Windows to Windows 10, the setup file automatically creates a new folder called Windows.old and moves files and folders belonging to the previous Windows version into the Windows.old folder.
The files and folders in the Windows.old folder is used if you decide to downgrade to the previous version of Windows 10 for some reasons.
The previous Windows installation files present in Windows.old folder usually takes at least 10 GB of disk space. So, after upgrading to a new build of Windows 10, you can delete the Windows.old folder to free up a good amount of drive space.
You likely know that deleting Windows.old folder is quite easy and possible using the Disk Cleanup utility present in Windows 10. But would not it be nice if you could make Windows 10 to automatically delete the Windows.old folder to free up space?
In Windows 10 Fall Creators Update (version 1709) you can configure the Storage Sense feature in Windows 10 to automatically delete previous Windows installation files.
The Storage Sense feature will automatically delete previous Windows installation files after 10 days of upgrading to the latest version. In other words, you will have ten days to roll back to the previous version of Windows 10 as you cannot perform a downgrade or roll back to the previous version without these previous Windows installation files.
Automatically delete previous Windows installation files in Windows 10
Here is how to configure Windows 10 to automatically delete previous Windows installation files.
IMPORTANT: This feature is exist in Windows 10 Fall Creators Update and above versions only.
Step 1: Open the Settings app. Navigate to System > Storage.
Step 2: Turn on the Storage Sense feature. Click Change how we free up space link.
Step 3: In the resulting page, in the Free up space now section, check the box labeled Delete previous versions of Windows option. That’s it!
By the way, to clean up those files manually right away, select Delete previous versions of Windows option and then click Clean now button to start deleting previous versions of Windows files.
In addition to automatically cleaning up Windows.old folder, the Storage Sense also comes handy to automatically delete unused files from Downloads folder.