How to delete the Windows.old folder from Windows 10 or Windows 8

To remove Windows.old files, we must follow these steps:

• Press windows button and type or search for “Disk Cleanup”  and launch disk clean desktop app. ​This may take little time as Disk Cleanup scan the files before loading.
• There are two sections on loaded popup. files to delete and clean up system files. 
• Click on Clean up system files. Again this may take little time to scan the files you can see the progress in pupup. Files to delete section will refresh with previous installation, windows updates files etc.
• Check “Previous Windows Installation(s) from the list and click OK.  You can check any other files if you want to delete them too.
• Click Delete files button from confirmation popup which says “Are you sure you want to permanently delete these files?”.
• Let the Disk Cleanup scan for files.
• Click yes button from confirmation popup which says “If you clean up the previous Windows installations or temporary installation files, you will no longer be able to restore the machine back to the previous version of Windows. Are you sure that you want to do this?”. you can change your mind too as you can’t restore them once deleted.
• Let the Disk Cleanup delete the files. Thats it.