I had the same problem too. I tried the diagnostic mode with no help, then I tried to manually install vc++ 2005. That also didn't help. So I uninstalled vc++ 2005 and ran revit setup. This time it installed the vc++ 2005 but crashed when it came to vc++ 2008. So I then decided that it wanted to install them all from scratch and proceeded to uninstall all versions of vc++ (both x86 and x64). Once done I ran the setup again and it has just successfully installed. So if you are having problems with the vc++ error then uninstall all instances of it including any that may have been installed by revit.