How to have tabs in IE 6

I've just noticed that my Internet Explorer 6 had tabs at work. I'm pretty sure that the original IE 6 does not have tabs. So how did I manage to add this feature in my IE 6 installation ?
I just tried IE 8 beta one on that machine - which was still running IE 6 for testing puposes. Then I decided to see if I could go back to my original IE and asked windows to deinstall version 8. To my surprise the uninstaller was present and did not really say no to deinstall. uninstall wen fine and I frist checkjed that IE was back to version 6.
It just took me a while to realize that I had gained tabs in the UI.