We recommend that first-time Pi users start by downloading and installing our New Out of Box Software (NOOBS) onto a 4GB (or larger) SD card. On first boot, this presents you with a choice of operating systems to install, including Raspbian, Pidora and two flavours of XBMC. Once you have installed an operating system, you can return to the NOOBS interface by holding down shift during boot; this allows you to switch to a different operating system, or overwrite a corrupted card with a fresh install of the current one.
By default, NOOBS will output over HDMI at your display’s preferred resolution, even if no HDMI display is connected. If you do not see any output on your HDMI display or are using the composite output, press 1, 2, 3 or 4 on your keyboard to select HDMI preferred mode, HDMI safe mode, composite PAL mode or composite NTSC mode respectively.