SQL Server 2012: Error while enabling Windows feature : NetFx3, Error Code : -2146498298

Problem

You are installing a new instance of SQL Server 2012 onto Windows Server 2012.  During the installation, you see the following error:

Solution

• Install the .NET Framework 3.5 feature.  No need to install HTTP or non-HTTP activation along with this.

References

• Error while enabling Windows feature NetFx3

Notes

• You'll need the Windows Server 2012 disk or ISO.
• Routine installation will fail.  You'll need to Specify An Alternate Source Path to enable the installation to succeed.  You'll see this setting during the feature installation.  It's near the bottom of the panel.  Alternatively, you can also use a DOS shell command (see reference).
• After doing this and re-running the installation, you may see this error appearing:

  An error occurred creating the configuration section handler for userSettings/Microsoft.SqlServer.Configuration.LandingPage.Properties.Settings...

  If you do, no worries.  First, close the installation panel.  Then, navigate to:

  C:\Users\[YourUsername]\AppData\Local\ Microsoft_Corporation

  and delete the folder there that starts with LandingPage.exe_.  Then re-run the installation.