Here’s a question I get a lot about Windows 10. “After one installs Windows 10 does the prior OS remain?”
If you do an upgrade from Windows 7 or 8.1 to Windows 10, the files for your previous OS will stick around in a file called “Windows.old” on your C drive. But they won’t stick around forever.
Microsoft lets you switch back your previous operating system during the first 30 days. After that period, those files will be automatically deleted by Microsoft.