Resolving Error Code 0x800f0818: Installing .NET Framework 3.5 on Windows Server 2008 R2

To address the error code 0x800f0818 during the .NET Framework 3.5 setup on Windows Server 2008 R2, follow these structured steps:

1. Verify that the .NET Framework 3.5 feature is active in Windows Server 2008 R2. Navigate to Server Manager > Features > .NET Framework 3.5 to check its status. If disabled, activate it and attempt the installation once more.
2. Ensure the installation source, such as a DVD or ISO file, is present and reachable.
3. Examine the server for any outstanding updates or required restarts. Execute any pending updates and restart the server as needed.
4. Utilise the DISM command for installation. Launch the Command Prompt with administrative privileges and execute:

   dism /online /enable-feature /featurename:NetFx3 /all /source::\sources\sxs /LimitAccess

   Substitute with your source drive letter.

5. If the issue persists, consider repairing the Windows Server 2008 R2 installation via the original installation media. Initiate the system with the installation media and select the repair option.