When you upgrade from an old version of Windows, Windows keeps a 'C:\Windows.old' with your old files. You can delete this folder to free up some storage space. To do this, Search for Disk Cleanup, and click on the 'Free up disk space' shortcut. Next, click on 'Clean up system files', enable the 'Previous Windows Installation(s)' option, and run a disk cleanup. If this option does not appear, that means there is nothing to clean up.