Resolving Error Code 0x800b0100 in Windows Server 2003 R2

Here are some actions you can undertake to address error code 0x800b0100 in Windows Server 2003 R2:

1. Verify internet connectivity: Confirm that your server is properly connected to the internet without any disruptions in the network.
2. Restart the Windows Update service: Navigate to Start > Run, enter 'services.msc' and press Enter. Find the Windows Update service, right-click on it, and choose 'Restart'.
3. Utilise the System File Checker (SFC): Open the command prompt by going to Start > Run, type 'cmd', and hit Enter. Then, input 'sfc /scannow' in the command prompt and press Enter to initiate a scan that repairs corrupt system files.
4. Manually install the latest Windows updates: Visit the Microsoft Update Catalog, search for the most recent updates for Windows Server 2003 R2, download them, and install manually.
5. Reset Windows Update components: Access the Microsoft Support website, download the 'Reset Windows Update Agent' tool, and follow the prompts to reset the components of Windows Update.