If you are trying to figure out how to install Windows Identity Foundation run-time on windows 8.1 here are the instructions:
"In Windows 8 Windows Identity Foundation is installed (enabled) by turning a windows feature on in Control Panel > All Control Panel Items > Programs and Features > Turn Windows feature on or off the feature is Windows Identity Foundation 3.5. Installers linked in the answer above will not work on Windows 8"
Taken from (http://stackoverflow.com/questions/3001598/where-is-the-microsoft-identitymodel-dll)
If you try to install Windows6.1-KB974405-x64.msu you will get an "Installer encountered an error 0x80096002 The certificate for the signer of the message is invalid of not found".
