Quick tip: how to delete Windows.old folder

After an in-place upgrade in the latest versions of Windows (2008 and up), the installation keeps a complete copy of the previous operating system into a folder named “Windows.Old”, in case you’d like to revert the upgrade. This is a useful option, but it leave your installation with a huge wasted space on the disk.
Learn how to remove the folder without installing Disk Cleanup or rebooting.