When you try to install SQL Server 2008 R2 and get the following exception
System.Configuration.ConfigurationErrorsException: An error occurred creating the configuration section handler for userSettings/Microsoft.SqlServer.Configuration.LandingPage.Properties.Settings: Could not load file or assembly 'System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified. (C:\Documents and Settings\<UserName>\Local Settings\Application Data\Microsoft_Corporation\LandingPage.exe_StrongName_ryspccglaxmt4nhllj5z3thycltsvyyx\10.0.0.0\user.config line 5)
delete the folder
C:\users\<UserName>\Local Settings\Application Data\Microsoft_Corporation\
