latitute X300 ultraportable laptop

just got a latitute x300 computer with out a cd/dvd rom and without the OS. I'm trying to use my usb external cd/dvd rom to boot up an old XP OS but the computer is not recognizing it. It pulls it up on the boot order menu but when I select it doesn't do anything. Do I need a special external drive and do I also need to install it in the B/Day drive instead in order to boot? thanks.