This is strange! I received the following error message while installing the SQL Server 2012 CTP1. It appears this version of SQL Server could not be installed on a machine that already had other versions of SQL Server. Not sure the reasons behind it, yet to research on it, but it is frustrating to say the least; I am hoping this is only because it is a CTP release. Prior to SQL Server 2014 I was able to install more than one versions of SQL Server on the same machine!