Have you just installed the May 2019 update? In this case, more than 10 GB of data is wasted on your hard drive – we had 24.6 GB! On a laptop or tablet with a limited amount of memory, this can be quite overwhelming for your device.
If you have a computer with a large amount of available memory, you may not even notice this unusable data. It will persist for 1
These files allow you to downgrade for 10 days.
Upgrade between "builds" of Windows 10 – as with Windows 10 October 2018 Update on Windows 10 The May 2019 update will be treated in the same way as the upgrade to a completely new Windows operating system.
When you upgrade to a new build, Windows creates a Windows.old folder that contains the system files from your "old" Windows installation. This will allow you to "revert" to the previous build of Windows 10 if there is a problem with the new build.
RELATED: What is the Windows.old folder and how is it deleted?
However, this folder may occupy more than 10 GB of space on your hard disk. Windows will automatically remove it after 10 days, but you can remove it sooner to free up disk space immediately.
Warning : This should only be done if your PC seems to be working properly. If you have a problem with the new version of Windows 10 on your hardware, you can not revert to the previous build without reinstalling Windows after you have deleted these files.
You can go back to the last build of Windows 10 that you installed by navigating to Settings> Update & Security> Recovery and using the Getting Started button under "Back to previous version of Windows 10". This button is only available if the files are still available on your computer.
To delete the Windows.old folder with
If everything seems to be OK after a few days, you can do so before and remove these files. You do not have to manually delete the Windows.old folder, and you should not do so. Some of the system files to be removed are already outside the Windows.old folder anyway.
Starting with the Windows 10 update from April 2018, you can now delete these files using the new "Free up space" tool in the Preferences. To access it, go to Settings> System> Memory> Configure Memory Sensor or run it now.
LINK: Use the new Windows 10 Free Space tool to clean up your hard disk.
Check the other settings here. By default, Storage Sense also deletes files that are older than 30 days in your Recycle Bin when you run it.
Scroll down and check the "Delete previous versions of Windows" option. If you do not see this option in the list, you have either already deleted these files or have already deleted them for you.
 Click Clean Now to delete the previous versions of Windows and all other items to be removed with Storage Sense.
Note that the checkbox "Delete files in my download folder if they have been there for a longer time" is checked. This option removes files from your download folder, which you may not want to do. Otherwise, you can safely delete all data types here if your PC is working properly. Note, however, that the "Delete files in my recycle bin if they were longer than there" option deletes the files in your recycle bin.
Deleting the Windows.old Folder Using Disk Cleanup
You can also use the Disk Cleanup tool to clean up the data for you. Disk Cleanup is now outdated, but is still available in Windows 10.
To start, open the Start menu, search for "Disk Cleanup" and press Enter.
RELATED: 7 Ways How to Free Hard Disk Space on Windows
Click in the Disk Cleanup window "on the button" clean system files ". 
Enable the option "Previous Windows installation (s)" in the list. You can also check other file types that you want to remove from your hard disk to free up space.
Click OK when you have selected what you want to remove. Disk Cleanup removes the previous Windows installation files and frees up space on your hard disk.
If you need to return to a Previous build of Windows 10 After removing these files, you must have Windows 10 installed from an installation media reinstall an older build.