huh... ok jack, i think you just made a little error. i dl what i uploaded for you and it works.
the path are : Harrypotter512x512.blp
LoadingScreen.mdx
write it exactly like that and it should work. i think you keep the ''\'' and it didnt work because of that.
PS :
here is your loading screen VeljkoM. for the path, remove war3mapimported\ from both files.