Error Code 8007066A or 66A

This problem may be caused by system corruption on your computer. For example, your computer may have corrupted hard disk sectors, or an application may have overwritten the .NET Framework files.

To resolve this issue, try one or more of the following methods in the order they are listed.

Method 1: Fix MSI software update registration corruption issues

http://go.microsoft.com/?linkid=9666880

Method 2: Repair the .NET Framework

Method 3: Manually download and install the update

Method 4: Uninstall and reinstall the .NET Framework

.NET Framework cleanup tool :

http://blogs.msdn.com/cfs-file.ashx/__key/CommunityServer-Components-PostAttachments/00-08-90-44-93/dotnetfx_5F00_cleanup_5F00_tool.zip

For more information : http://support.microsoft.com/kb/2507641/en-US