Here is a Dell Knowledge Base Article discussing the Installation of Windows 10 from an ISO image.
Many people have been interested in downloading and installing Windows 10 directly onto their systems (via an ISO file), without doing an upgrade, using the Windows 10 download links provided by Microsoft. Without doing an upgrade first this is known as a "clean install". Many people prefer to do this as they've had unhappy experiences with Microsoft OS upgrades in the past.
Many people have been running into problems about the installation process asking for a Windows Product Key. We've created a quick KB article to discuss, linked above in this post.
One thing I really want to call out, and tons of people have experienced this firsthand over the past few days, is this note:
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NOTE: For a clean install of Windows 10 to activate, the system must have previously been upgraded to Windows 10 and the upgrade activated. Once this has been done, then a Clean install will also activate.
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I hope that the linked KB article will be kept updated as more information becomes available.