Ok, here's what this is-a American Megatrends mother board with Win10 Pro OS with MUP key (legit that allows volume dealers to install Win10 and activate it for end users). What it doesn't come with is any documentation and individual Win10 key although they supply it later by email. My unit had a corrupt file that would not allow File Explorer windows to stay open. Messaged through Amazon the vendor who within a few hours supplied both the Win10 Key and instructions with a video how to download and reinstall the OS. Doing that and then entering the key Win10 activated Win10 Pro without an issue. After reinstalling the OS it worked perfectly. Kudos for good support and well made product. It also accepted a second SSD drive without any issue.