Notes
You will need a computer running Windows XP or higher (We recommended
that you use Windows 7 or higher) to install Fiddler Classic.
Fiddler Classic is a free software to download.
Instructions
Follow the instructions below to help you set up Fiddler Classic to
troubleshoot Windows Update.
Download Fiddler Classic from its official website (don't worry, it's free).
Install it on a modern machine, running Windows 7/8/10 or 11.
Open Fiddler Classic. Go to Tools, Options, Connections tab and check "Allow remote computers to connect". Set the port to 8888 and save your changes.
On the client machine (running Windows Update), open Internet Explorer.
Go to Tools, Internet Options, Connections tab, LAN Settings, check "Use a proxy server", click Advanced.
In the dialog box, under "HTTP", enter the IP address of the machine running Fiddler, and the port (which is 8888 by default). Click OK, OK, but do not close the Internet Options.
Go to the Advance tab, and check "Enable HTTP 1.1 through proxy connection" in the list. Click OK to save your changes.
There you go! You should now be able to proxy what your client does, and find what's missing for Windows Update!
If you have any more questions or need further assistance, feel free to join our Discord server to get help from our members.