When trying to reinstall .NET 2 after a failed install/reinstall you may get this message.

error 25007. Error occurred while initializing fusion. Setup could not load fusion with LoadLibraryShim(). Error: 0x80131700

You will also go and do all sorts of stuff to get it working.  What they don’t tell you is:

UNINSTALL .NET 4 TOO AND REBOOT BEFORE REINSTALLING….