There are a number of ways you can recover the space after you upgrade to Windows 10. But this is the recommended way.
Before you release any files to recover space make sure you want to stay on Windows 10.
Some files you delete will preclude you from going back to the previous Windows release.
- Deleting the Windows.old folder.
- Open File Explorer
- Click This PC
- Chose the Windows Drive usually C: and right click Properties
- Click Disk Cleanup
- And then the Clean Up System button.
- Select the Previous Windows System Installations. You can select some other options.
- Click OK
- Delete Files
- And Finally Yes to compete the function.
This should make available about 10GB of space.