I am trying to install .Net Framework 3.5 (required by many applications) on a brand new out of the box Surface Pro 3 running Windows 8.1 64bit.  When I attempt to install I get the following message.

The following feature couldn't be installed .NET Framework 3.5 (includes .NET 2.0 and 3.0) Windows couldn't find required files to complete the installation...........

Error Code 0x800F081F

I am connected to the Internet.  I have tried accessing the source files via an external HD containing Win 8.1 installation files.  Basically I have tried everything that I have found on the Internet with no luck.  It appears that the problem lies in the fact that Security update KB2966826 is installed on the unit and was so when it was delivered.  There appears to be no way to uninstall this update.  I have reset the Surface Pro back to factory defaults several times the most recent being 7/23.  Since the update came on the unit it is installed at every reset.  I am looking for help with uninstalling security update KB2966826.

Thank you

Hi MLPHRP,

We could run "wusa /uninstall /kb:2966826" to uninstall the update. In addition, the KB2966827 and KB2966828 may also be related.
It is not recommended to uninstall any security updates. Please install them again once you have installed the .net framework 3.5 successfully.
Here is a link for reference:
0x800F0906 and 0x800F081F Error Messages While Installing .NET Framework 3.5 in Windows 8/8.1
http://www.askvg.com/fix-0x800f0906-and-0x800f081f-error-messages-while-installing-net-framework-3-5-in-windows-8/
NOTE: This response contains a reference to a third party World Wide Web site. Microsoft is providing this information as a convenience to you. Microsoft does not control these sites and has not tested any software or information found on these sites.

Best regards