Error Code 66A

Trying to download a Windows 7 update called: Security Update for Microsoft .NET Framework 4 on Windows XP, Windows Server 2003, Windows Vista, Windows 7, Windows Server 2008, Windows Server 2008 R2 for x64-based Systems (KB2518870) but I keep getting an error called Code 66A and it will not install. Any idea what I can do? I ran the Windows Update Troubleshooter but it wasn’t able to fix it.

You might try this.

The tool apparently can remove all .NET versions so be sure pick to only remove version 4. Then rerun Windows Update and it should recommend .NET 4 nd it's updates.