Step 1: Click on the Windows search bar or press the start key on your keyboard, type cleanup, then select Disk Cleanup.
Step 2: Click ‘Clean up System file’
Step 3: Scroll to, and select, Previous Windows Installations. Click start to begin the cleanup process which will include the removal of previous Windows installations from your disk.
This freed almost 30Gb on my disk. This, of course, means you’re unable to revert back to your previous Windows installation so proceed with that in mind. I found the disk space more valuable than holding on to the files.