When I used to do tech support, from Win 98 all the way through Win 7 days, I would consistently find that reasonably intelligent human adults had difficulty understanding the Start Menu. If something wasn’t on the first menu, they weren’t going to interact with it. It seemed like such a no-brainer to me — just expand the folders! — but a staggering number of people found it alien and never adapted. Even the idea of a right-click VS left is too much for many people.