Download and install .NET Framework from http://www.microsoft.com/net and then rerun Setup.
The error message resembles the following:
Error messages in SQL Server Setup log files
When you examine the Sqlsetup.log that is located in the temporary files folder (%temp%), you see entries that resemble the following:
Note The Microsoft .NET Framework 4.0 is made up of the .NET Framework 4 Client Profile and the .NET Framework 4 Extended components. These components exist separately in the Programs and Features item in Control Panel or in the Add or Remove Programs item in Control Panel in earlier versions of Windows.
This problem was first corrected in Microsoft SQL Server 2008 Service Pack 3.