I found the problem for httpsproxy. Here my solution:
Close httpsproxy. Delete all Certificates from the folder "Certs". Delete the generated Certificate from httpsproxy and replace it with mine and run the Certinstaller. Call up Windows Update again and try to search for updates.
It works fine for me.
HTTPSProxyCA.crtProxHTTPS Cert Install.exe
You need to add these three websites to Trusted Sites: http://www.update.microsoft.com https://www.update.microsoft.com and http://update.microsoft.com
And set the level to high. If it is not available, press reset first.
Let's forget that for now. I'll explain again once we find the certificate error.
I think we're all talking past each other now. I have the program from ThomasS. It runs directly in the Xp Vm.
The certificate error photo is of my vm and is enabled because it worked with ProxhttpsProxy, only with httpsproxy I get the error. The photo with the validation is from a real computer.
I did exactly the steps that were shown to me. I also replaced the configuration file. I can access all websites except check for updates. Certificates are also installed.
Same problem in Win 7 too:
@Dave-H Try ProxhttpsProxy and replace the configuration file and start Windows Update or Microsoft Update. Don't forget to install the certificates! http://i430vx.net/files/XP/ProxHTTPSProxyMII_REV3d_PY344.7z
config.ini