There are so many tasks on a computer that are just fundamentally broken for a large number of users because they don't get the concept of files in folders and applications that interact with these files. Programmers (myself included) lazily assume this knowledge instead of thinking about what a user might want to do. "I want to listen to a song" shouldn't involve the user picking a nice place on their disk to store this particular song, and ideally the browser and music player just work together to 1) open the song and 2) make it available from within "music" whenever the user wants to hear that song again.
This is especially painful when having to explain to others how an overly complicated (which most of the time means dumb) piece of software (windows, itunes, any antivirus) works, and more often than not I resort to "just bring the pc over, and I can do it in five minutes for you". As a developer, I feel shame whenever I have to update my mothers iPhone or reinstall my grandmothers computer because we can't make something that takes their needs into account. (Regarding the last: ever tried globally enlarging text on windows for bad eyesight? It obscures so much text in incorrectly sized buttons that it might as well be non-existent.)