In the past, Microsoft partnered with Digital River to host ISO files. Many of these links are still functional but are buried deep in the archive.
. While you can no longer find a direct "Download Vista" button on the Microsoft Download Center Windows Vista Iso Download Microsoft
Microsoft previously offered a “Software Recovery” page where you could download ISOs by entering a product key. That tool now only supports Windows 7 and later. In the past, Microsoft partnered with Digital River