Microsoft .NET Framework 4
The Microsoft .NET Framework 4 web installer package downloads and installs the .NET Framework components required to run on the target machine architecture and OS. An Internet connection is required during the installation. .NET Framework 4 is required to run and develop applications to target the .NET Framework 4.
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=9cfb2d51-5ff4-4491-b0e5-b386f32c0992