In response to a user instruction to initiate media playback, which instruction may come from a dedicated media playback hardware button or from a user interface on a display screen, a computer operating system activates a predesignated media playback user account. The account may be limited to access of media playback applications and files located within shared directories. The operating system also launches a media playback application in response to the user instruction to initiate media playback. Instead of activating an account in response to a media playback instruction, the operating system can execute a media player application within a login screen.