I just wanted to add that I had the same problem, but the Microsoft autoplay fix didn't work, and I didn't have Real Player installed. In my case, the problem was a Nero suite I had installed. I had to uninstall Nero PhotoShow (or something like that - it's the photo program), then autoplay worked.
Thank you for the comments here about Real Player, or I would have never thought to look for it and, in the process, realize Nero has a photo program.

