Ok,two possible solutions.
Just Alt+Tab out of the black screen to switch to a new screen. Afterwards, Alt+Tab back into it, then hit Esc. The main intro should start right up. This works with Vista although xp should be no different.
Assuming you have installed Call of Duty World at War in it’s default installation directory :
Navigate to C:\Program Files\Activision\Call of Duty - World at War\main\video and delete “Treyarch.bik”. This video file has been causing lots of problems.