|You don't need to go into the BIOS Setup. There's a temporary Boot Menu that you can invoke by pressing the <Esc> key repeatedly as soon as you turn your netbook on. |
From the menu you can choose your preferred boot device as a "one off". This preserves the existing boot device sequence which appears in BIOS Setup.
The external DVD drive must be plugged in and working, otherwise it won't appear in the Boot Menu.