External dvd-rw

Hi

My brother bought a external dvd rw because the computer he uses only has a cd rw, it plugs n by usb port. The cd rw is called drive D, when he put a dvd in the dvd rw it comes up drive E. When he goes to burn a movie it wont pick up drive E but only pick up drive D which is the cd rw. I dont think it came with any drivers and he is using windows xp server pack 3. Can anyone suggest how he can get it to pick up the external dvd rw (DRIVE E) when burning? Thanks