If you install Microsoft SQL Server 2012 on a Windows Server 2012, you may get the following error message during the installation:
This error message appears because .Net Framework 3.5 is not installed on the Windows Server 2012. Open the Server Manager, start the “Add Roles and Features Wizard” and install the .NET Framework 3.5:
By default the .Net Framework 3.5 is not installed and you should point to the sources of the Windows Server 2012 in order to be able to install this feature. You can specify an alternate source path. Note that the .Net Framework 3.5 is located in the d:\sources\sxs\ folder where d:\ is the Windows Server 2012 source dvd (or loaded iso file if you use a VM). The SxS folder is the side-by-side store folder.
Make sure you do a reboot and then everything should work fine…