You'll have to replace the door because cutting it in half would leave holes in the bottom of the upper half and in the top of the lower half. (That's because the door is hollow.) You'll also have to add more hinges. The 2 doors (upper and lower) will require at least 2 hinges each. That probably means doing some work on the trim and frame as well.
[This message has been edited by rpxlpx (edited June 26, 2002).]