Up-loading > Down-loading

I burnt a video file onto a DVD+Rw 1-4speed succesfully using Win DVD, then I deleted the file off my hard disk. Now I want to copy the DVD back to my hard drive but it will not do so. WHY ? Do I have to purchase an external device of some sort.
The computer has a “hp dvd writer & cd writer > +R / +RW 8x
Regards jasper_2x