If you installed the new one Windows 10 version Anniversary Update over a previous one version of Windows, you would notice that your free disk space has decreased significantly.
By upgrade from a previous version of Windows, Windows 10 saves many files from the previous version during the duration of the upgrade, and thus your hard drive is filled with files that you may not need again, especially if your upgrade was successful. 
Setup saves these files, just in case something goes wrong with your OS upgrade. If something goes wrong you can reset me better safety the previous version of Windows.
But if everything works perfectly, there's no reason to keep junk in the computer you.
Below we will see how you can free up space after upgrading your operating system (Winaero):
Tap the two Win + R keys to open the Run dialog.
Enter the command and press Enter:
cleanmgr
Select the disk it is installed on functional (usually it's in C) and press OK.
Click the Clean up button to activate it tool Liquidation disk.
Find and select the files of the previous Windows installation (Previous Windows installation(S).
Click OK and you're ready.
