When you update
your computer to the latest version of Windows
10, then you will see the installation process save a copy of the previous version
in the "Windows.old" folder.
This is part of the security mechanism in the upgrade process. If installation
failed for any reason, the system can use the Windows.old folder for
cancel change. Also, if the update is completed successfully, copy
a backup of the previous version will be saved to provide options for
recover if at any time there is a problem with the newly updated version.
Even though this is a practical feature, and your computer is functioning normally after the Windows version upgrade, you can delete the Old Windows folder. This Old Windows Folder Removal can be considered safe and can increase the capacity of your hard drive.
In this guide, we will guide you on how to delete the Windows.old folder with SAFE:
Step 1: Click on Windows search,
type Cleanup then click Disk Cleanup .
Step 2: Click the button "Clean up system files"
Step 3: Wait a moment
Windows scans the file, then scrolls down until you see "Previous Windows
installation (s). "
Step 4: Check the box next to the entry, then make sure no other boxes are checked. Click  OK to start deleting Old Windows Folders.
As you can see from the screenshot above, Windows 10 I use almost 25GB of my hard disk space. The size is quite large!