When running Windows Update in Windows Server 2003, Windows Update may fail with the error code 0×80190191. This could be caused by the winHTTP Web Proxy Auto Discovery Service.
WinHTTP implements the client HTTP stack and provides developers with a Win32 API and COM Automation component for sending HTTP requests and receiving responses. In addition, WinHTTP provides support for auto-discovering a proxy configuration via its implementation of the Web Proxy Auto-Discovery (WPAD) protocol.
To resolve the problem, stop this service and run the Windows Update again. To stop the service,
1. Click Start – Search for Services.msc and press enter.
2. In the right-pane, scroll down to the “winHTTP Web Proxy Auto Discovery Service“. Right-click and select “stop”.
3. Now, start Windows update and should run without errors this time.