Internet Explorer 11 Gains HTTP Strict Transport Security In Windows 7 and 8.1
Mark Wilson writes: Anyone using the Windows 10 preview has had a chance to use the HTTP Strict Transport Security (HSTS) in Microsoft Edge, and today the security feature comes to Internet Explorer 11 in Windows 7 and Windows 8.1. This security protocol protects against man-in-the-middle attacks and is being delivered to users of older version of Windows through an update in the form of KB 3058515.
You forgot a step. ..load a fresh Windows install, open IE, deal with the security settings for your profile, then download Firefox.
That's why I load a fresh Windows install, open the command prompt, FTP to ftp.mozilla.org, and download Firefox.