This video shows how to update to Sony's official firmware 5.03.
Further info at http://lgallardo.com/en/2009/05/10/como-actualizar-el-psp-al-firmware-503how-to-update-your-psp-with-503-ofw/
Watch the Spanish version here: http://lgallardo.com/2009/05/10/como-actualizar-el-psp-al-firmware-503how-to-update-your-psp-with-503-ofw/