If you have already installed the evaluation version and have a valid product key, you do not need to reinstall. You can convert it to the full Standard edition using the tool in an elevated Command Prompt or PowerShell: Check current edition: dism /online /get-currentedition
To obtain a non-evaluation (Retail or Volume License) ISO for , you generally need to access specific Microsoft portals available to licensed customers. Official Download Methods Windows Server 2016 Standard Iso Not Evaluation
Log into the or the Microsoft Volume Licensing Service Center (VLSC) . If you have already installed the evaluation version
Open Command Prompt as Administrator and find the index number for "Standard Evaluation": Windows Server 2016 Standard Iso Not Evaluation
Ensure firewall ports (TCP 1688 for KMS) are open if you are activating via internal corporate servers.