We use a touch screen interface on XP without any problems. It deos mean that the software has to be written to take adavanatge of touchscreen techniques (bigger finger sized buttons), pope up keypad, again finger sized.
the finger acts as a mouse so pointer use ins't that much of a problem, you can run a mouse as well as the touch screen concurrently, you can also have a keyboard connected as well.
the rest of it is up to you.....