Well the first thing that come to mind, would be an extension they didn't recognize and couldn't open? Like .ppt but they don't have PowerPoint installed. Of course, this somewhat refutes my earlier comment as well, because most of the unrecognized extensions might be more technical in nature.<p>Perhaps there should be a top sections with something like: "I like it dumbed down for me: .abc is a abc application file" and a section below that for "I'm 1337, give it to me straight: this .abc file is a windows me executable with blah blah blah..."<p>Aside from choosing better titles for the sections, that might be more helpful to everyone. All of the file detection only needs to be done once.