RE: Download Windows 7 - No disk but have product key
What model of Dell?
You can download a Windows 10 Version 1809 ISO from Microsoft and make a Bootable USB. Windows 10 Installation Media will work with your Windows 7 Product Key (this still works despite the initial 1 year marketing). Windows 7 Reaches End of Life in January meaning it will have no more Updates and be an insecure Operating System.