I have been trying to install the KB958481 patch for Microsoft Dot Net Framework 2 for many hours. Each time the installation would fail with “The installation failed with: This patch package could not be opened. Verify that the patch package exists and that you can access it, or contact the application vendor to verify that this is a valid Windows Installer Patch Package.”
Of course the patch file exists (I am installing it after all) and the patch file came from Microsoft so I would hope it’s valid. Most of the suggestions seemed to resolve around removing the dotnet framework and reinstalling. All of which I had done in a variety of ways. First by uninstalling the software through add/remove programs and then through Aaron Stebner’s dotnet cleanup tool – neither of which solved the problem.
Eventually I stumbled across a tech posting (made after my initial problem started) in the Microsoft forums (first and second posting that mentioned installing the Microsoft Installer 4.5 redistributable component. After an initial reboot before installing, a reboot after installing, installing the .net patch and another reboot afterwards I was up and running and able to install the other .net patches too.