Which habits of other people make you cringe?

My dad refuses to use bookmarks in his browser. I finally convinced him to switch to Google Chrome (he's coming from IE 7) recently but instead of using bookmarks or even google his way to his most visited websites, he has learned to put a shortcut on his desktop. Now his desktop is filled with links to websites, resulting in a sea of Google Chrome icons.

Another thing that "grinds my gears" is that he double clicks EVERYTHING. He's been using a computer for over 5 years. Watching him navigate to his e-mail is pure horror every time...

What are things people do that make you die a little inside? It doesn't have to be IT related of course.