What do you mean by external, do you mean like a Laptop External DVD drive, if that is the case, then yes you can.
If you mean a Stand Alone DVD player that normally outputs to a TV then, it is all dependent on the Video In hardware that you (or your friend) has. Basically I think it should be possible, but if its a stand alone player then you wont need any DVD player software as that is only used for software decoding of the DVD and the output of the content. A stand alone player does all of that for you, all you would need is some software capable of displaying the video input and this software should be included with the Video In card.