How To: Troubleshoot Microsoft.Net Framework installation issues
When Microsoft Windows Installer is incorrectly registered in the Windows registry, the .NET Framework version Setup program cannot gain access to some Windows Installer components. The below articles discuss how to work around this issue by unregistering and then reregistering Windows Installer.
We may not always be able to completely remove the .NET Framework version by using the Add/Remove Programs tool in Control Panel. The below articles also discuss how to work around this issue either by manually removing the .NET Framework version from your computer and then reinstalling the .NET Framework version, or by repairing the .NET Framework version.