Modern hardware has outpaced Windows 7. If you are trying to install a Dell Windows 7 ISO on a new Dell machine (post-2018), you will face significant hurdles:
Go to dell.com/support , enter Service Tag → "Drivers & Downloads" → OS = Windows 7. If no drivers listed, the system is not supported. dell windows 7 iso
Download and install the tool from the Dell Support site . Modern hardware has outpaced Windows 7
Given Windows 7's end-of-life status (as of January 2020), Microsoft no longer provides security updates or support. This makes it less secure to use compared to newer versions of Windows. If your Dell computer supports it, consider upgrading to a newer version of Windows for better security and support. Download and install the tool from the Dell Support site
If you have legacy hardware (like a Dell OptiPlex 7010 or Latitude E6430) that runs best on Windows 7, do not download a random ISO from a file-hosting site.