according to Dell if bios is updated to A12 or newer in Inspiron 20 (3043) All-in-One, it should be easy to see cd rom/dvd drive in boot list once Legacy Option Roms was enabled,  the following options became available in the one-time-boot menu. [IMAGE] without the hassle of selecting file path.  
I've been trying to boot from my external DVD drive but I have problem adding the DVD drive to my boot option. I've read post on adding DVD drive to boot option but mine is still requesting for file path after selecting it's (DVD-rw drive) file system. Bios version a06
Add DVD re drive to boot option bios a06