How to fix Unable to Complete Secure Transaction error in Opera web browser in Windows
WARNING - I will NOT be held responsible for any damages the software(s) and methods shown in this video may cause to yours or someone else's computer, hardware, software, and/or data, including loss of use of such devices and/or loss of data and/or loss of profits from the resulting inability to use such devices and data. Any information or program you choose to put into use from this video is done AT YOUR OWN RISK. As a precaution, I recommend backing up any irrecoverable data before installing and using ANY new software(s), including those shown in this video.
This video will show you how to fix the Unable to Complete Secure Transaction error when trying to connect to HTTPS websites using an older version of the Opera web browser on Microsoft Windows. The Opera developers have developed a newer version of the Opera 12 browser (the classic browser built upon Presto) with new security certificates that will allow users to view HTTP secured websites with no pesky 'unable to complete secured transaction' error messages.
Official download link:
http://www.opera.com/download/guide/?ver=12.18
Footnote: Clicking on Opera - Settings - Preferences - Advanced tab - Security and changing Auto-Update to 'Do not check for updates' will avoid Opera harassing you to update to the modern Opera browser during subsequent browsing sessions.