If you have a product key for Windows 7, you might be able to use it to obtain the ISO directly from Microsoft, though their support for older versions like Windows 7 has ended.
Given Windows 7's end-of-life status (as of January 2020), Microsoft no longer provides security updates, making it a risky choice for continued use. Consider upgrading to a more modern version of Windows for better security and support. windows tiny 7 iso download
If you're looking for lightweight operating systems or ways to breathe new life into older hardware, consider these alternatives: If you have a product key for Windows