Did you upgrade to Windows 10 or install a new Insider test build? Then use this guide to get rid of the Windows.old folder that is only wasting gigabytes of space in your PC's hard drive.
Every time you upgrade your PC from an older version of Windows to Windows 10 without first formatting the hard drive, or when you install a new Windows Insider Preview test build, the install wizard will save a copy of the previous version inside of the "Windows.old" folder on your computer.
This copy is a safeguard mechanism in case something goes wrong during the installation process. If something bad happens, the operating system can use the backup copy to roll back any change automatically. Or in the case of Windows 10, you also get the option to go back to your previous version of the operating system within the first month if you don't like it.
If everything is working as expected after upgrading to Windows 10, you probably don't need these files, as they will just be wasting precious hard drive space. In this Windows 10 guide, we'll walk you through the steps to delete the Windows.old folder and other files that can be taking more than 15GB of storage space on your computer.
How to delete the Windows.old folder on Windows 10
The Windows.old folder resides in the hard drive where the operating system is currently installed (typically the C: drive). However, you can't just hit the delete key and to make it disappear, you need to use the Disk Cleanup tool.