Answer:
Hello! When reinstalling the operating system for your computer, if you don't format the drive (drive C, the drive where you install Windows), then after installation, a Windows.old folder will appear. This folder contains data from the old operating system. You can delete them if you have backed up your data before installing. However, you cannot delete them normally (Delete or Shift + Delete), you have to do it in the following ways:
Method 1: Delete the Windows.old folder using the Disk Cleanup tool available on the operating systems:
Method 2: Using a command to delete the Windows.old folder: